Credit: xHypex, Mishmosh, and Keven97SE

General Tools:

1/4″ and 3/4″ socket sets with extensions.
Have a magnet antenna handy.
Wear gloves when breaking bolts loose.
Optional: vacuum gauge to measure manifold vacuum levels before and after (Should be 18-22inHg roughly, and identical before and after the install).
Stay Organized as there is a lot that comes off the manifold that will need to be replaced on the new VI. Keep bolts/gaskets/tools together in an organized fashion.

VI ASSEMBLY

Unpack your VI and misc parts. Quickly identify what parts are used for what. Consult the schematic for bolts that look similar.
Start by inserting the O-ring into the outer right depression where your rod will insert.
Lube contact points on the rod and insert into the VI. Make sure the Right end of the rod will rotate and touch the contact plate on the VI.
Install all 6 butterfly valves using the smallest screws, 2 for each valve. You may want to dab some silicone adhesive or Loc-Tite on the threads to insure that they will not break free.
Align cover gasket and collector cover using the 9 cover bolts.
Attach the vacuum lever to the VI (2 bolts), making sure the end connects to the rod end properly to rotate the valves open and closed.
Unscrew the brake booster vacuum port from your stock manifold and install it on the VI, maintain proper orientation.

STOCK MANIFOLD REMOVAL

(Order not strictly important in some cases)

(bolts are 10mm and 12mm)
disconnect all connections coming of the rear harness that overlies the manifold. You do not need to label these as their position, size, and color will guide reinstallation.
unbolt all brackets on the top of the manifold. Replace each bolt you remove immediately to their corresponding position on the new manifold to keep organized.
swing harness off the the left and out of the way.
Unhook throttle and cruise cables and their brackets.
PCV tubing: Unclamp the hose leading to the PCV where it attaches to the manifold and remove the entire unit (including PCV valve). You can choose to install in on the VI at this point or set it aside.
TB: Loosen and remove the 4 retaining bolts. Handle the gasket with care as it is thin and can easily be cracked. If it is stuck on, release it with the tab that is on one of the edges. You do not have to remove the intake hardware.
IAC: Loosen and remove the 3 retaining bolts. Before you can remove the upper rear bolt, you will need to remove the 10mm bolt that holds in the bracket that impedes access. Let the bracket fall as it is held by leads that are attached to the EGR guide tube. As with the TB, handle the IAC gasket with care. If it is stuck on, release it with the tab that is on one of the edges.
EGR guide tube: should now be in view with the IAC unit removed. It is held in by two bolts with two fat washers–make sure you secure the metal gasket and washers as you pull out the bolts.
Rear Manifold retaining bolts. Located on each side at the rear of the manifold. They are near impossible to see and need to be felt. I would recommend a 1/4″ ratchet with 12mm socket.
Front retaining bolts: remove all five 12mm bolts along the front ports of the manifold.
Coolant hoses. You will want to do this LAST. Just below the EGR guide tube are two coolant hoses. You need to try to rotate the clamp so that you can loosen them with pliers by squeezing the tabs and remove the hose. Lift up the end of the manifold to give yourself room. Very little coolant will leak out once done.

VI INSTALLATION

first, place the new upper-to-lower manifold gasket in the proper orientation and alignment (with tab in front and to the left).
carefully place the manifold ports over the gasket while making sure the rest of the manifold is fitted properly in place at the same time. You may find it useful to remove the cylinder bolted to the firewall that the cruise control cable is attached to, so as to facilitate proper placement of the rear of the manifold. Before you install the 5 front retaining bolts, you will need to thread in the two rear retaining bolts. Hold the front ports in place over the gasket by installing and loosely tightening only the left and right front bolts. You will probably need to vary slightly the position the rear of the manifold to thread in the two retaining bolts.
reverse the order of manifold removal (above) for reinstallation of the rest of the components.

RPM Vacuum Actuator Subsystem

Required components: RPM Switch (ie. Harlan), Relay, Control Solenoid, Vacuum canister, one-way check valve (if not built into canister), ~3ft rubber hose (no greater than 3/16″ I.D. but preferably a tad smaller than that, if available), one 3/16″ T-piece.
RPM Switch: Positioning the RPM Switch is done by personal preference. You may find that if using a coil pack input signal that an engine bay location (ie. near relay box) may be preferable and that if using the TAM screw in your gauge cluster that a *****pit location may be preferable (ie. gearbox, underneath dash, etc.).
Relay: Connect the Switched Ground from the RPM switch to the ground of your relay. Connect the car’s 12VDC supply to the 12V switch input and supply terminals on the relay. The 12VDC output on the relay will connect to the control solenoid. The relay serves to convert the RPM’s switched ground output into a switched 12VDC line, so that the solenoid does not ground through the limited power capability of the Harlan circuit.
Control Solenoid: powered by the switched 12VDC line from the relay and grounded to the car’s ground. A pair of grounding bolts is conveniently found just in front of the intake manifold which can serve this purpose. The main vacuum line of the solenoid should attach to the vacuum lever of the VI (“the golden globe”-like object). The default port of the solenoid is left unterminated, open to air. The switched port of the solenoid is connected to the vacuum canister output.
Vacuum Canister: Supplied by manifold vacuum. If your canister does not have a built in one-way check valve like the NAPA unit (large nipple is the input, small nipple is the output), then insert a one-way check valve in between manifold vacuum and the canister input. Make sure the directionality is correct (ie. flow of air TO the manifold vacuum source).
Manifold Vacuum: Many potential lines are available for T-piecing. I suggest the Fuel Pressure regulator which is close proximity to the front right corner of the VI.

TESTING

Test the Harlan RPM switch for proper capture of either the coil/Tach line. When setting values, make sure you press each settings button for >2sec. It is desirable to set the RPM set point low for easy testing (ie. 1000rpm). Even without connecting anything to the Harlan, the LED on the circuit board will light when the switched ground is activated at the programmed set point.
Test the vacuum system to insure that the canister is producing suction at it’s output. Simply start the car and put your finger on the canister output and feel for suction. The vacuum canister should store vacuum that is equal to manifold vacuum.
Test solenoid function by either connect a 12VDC line from the battery (with car idling and vacuum system connected), or after the whole system is set up, by pulling on the throttle cable and watching the VI vacuum lever activate (again, test set point of 1000rpm on the Harlan).

Pictures

Mishmosh

Directly facing the IAC, this pic of the right side of theIAC shows the 10mm bolt that you need to remove to get the bracket out of the way of one of the 3 retaining bolts. That cable you see is connected to the EGR guide tube.

shows some butterfly’s installed. Pay particular attention to how the end of the rod lines up with the stopping plate (on the right). The butterfly’s are not sided so any side is fine. The rod has one side rounded and the other flat so there is no question which side to mount the valves.

Rear retaining bolt that you need to feel out and remove. 12mm

Side view with the stock intake manifold out. Key structures: Mounting brackets for the two manifold retaining bolts. EGR guide tube. Rear coolant hose. TB/CAI. throttle/cruise cable along firewall with that cylindrical structure attached to the firewall (which I removed cause it made position the new VI a little difficult).

Right rear side pic showing EGR: note the 12mm bolt and the fat washer. In the lower right corner of the pic, you can see the coolant hose. There is also another one on the other side of the EGR (out of view).

Side view of the installed vacuum actuator. Manifold vacuum fed from the Fuel Pressure Reg vacuum line down below >> Vacuum canister >> Switched port of the solenoid >> main port of the solenoid to VI vacuum lever.

Ground bolt–a convenient place to ground. (Credit: xHypex)

Relay that activates MAP switch. Can you tell which it is? (I don’t have ABS)

Vacuum Canister mounted near the strut mount (it will be painted soon)

Nissan vacuum canister adds to the OEM look

Nissan MAP switch

Nissan Check Valve connected to the FPR vacuum via a F fitting

After installing the VI your EVAP will not have a place to mount. On the ’99s the EVAP is a small electrical sensor and sits nicely on top of the manifold. 95-98s have a mechanical EVAP which is larger.