This is the worst part. The little movable slats are mounted on a plastic ring, and the ring

is pushed into the hole. Two "fingers" snap against a ridge on the hole in the dash, and keep the slat ring from pulling out if you pull it straight back. If you are lucky, you can get a small screwdriver behind the two fingers, pull the fingers inward (toward the center of the opening) and the vent will pull straight back and out. BUT, sadists that GM folks can be, the fingers are right behind where the center post in the slat ring is mounted, so you really have to finagle the screwdriver. It appears the front part, with the vertical post, and the slider is separate from the inner ring with the slats, and that possibly you can pull the two larger taps down to release the front ring, making it easier to work on the back ring. I have to look at this more.

After a lost of frustration, I took a pair of pliers and broke the center ring out. The second one came out a bit cleaner, because by then I had found the "fingers"

Now you have two holes in the dash. The 2-5/8" Auto Meter gauges fit like a glove. You might even have to sand the openings very lightly, but try it first by just pushing the gauge into the hole. You can always reach in through the other open hole and push it out. After you are satisfied that the gauges will fit OK, its time to start the wiring and other connections.

Wiring/Hoses/Lights/etc.:

You will have a variety of stuff to pass through the back wall of the A/C duct, including the wires for the electric fuel pressure gauge, the hose for the mechanical nitrous pressure gauge, and the lighting power for both of them. By the way, put the little red "condoms" on the gauge bulbs....the red looks great with the Trans Am or Formula dash lighting.

You will need one hole in the back of the plastic A/C duct. I used a 1/2" wood bit, because it was very long, and I could reach the back of the duct through the vent opening. I put the hole sort of 1/2-way between the two openings. Be sure you don't let the drill go too far through the back of the duct. I felt back there and there wasn't anything in the way, but who knows if all the cars are alike.

First run the -3AN for the nitrous pressure gauge through the hole, because the end connection is the largest thing that goes through the hole. Now take the power and ground wires for the bulbs and splice them together so you only have one power and one ground wire to run. I used the first metal bracket screw I saw for the ground, and ran the +12V line to the connector for the fog lights (my Formula does not have fog lights) just below the headlight switch. That way the gauge lights will only come on when you turn on the headlights, at least that's the way mine work. When you push the wire through the hole in the duct, they will flop out far enough far you to reach them and route them whichever way you want to go.

For the fuel pressure gauge, I used the NOS -4AN swivel 90 off the Schrader, through a short -4AN hose to a brass tee. I put the fuel pressure sending unit and my fuel pressure safety switch on the tee. The wires are routed to the rubber grommet behind the computer, and into the passenger compartment. You have to pull the side plastic off the passenger foot well. The wires go to the electric transmitter box, which is double face taped to the A/C duct above the passenger's feet. A ground goes to the nearest metal bracket/screw, and power is taken from the switched accessory connection on

the fuse box on the driver's end of the dash.

The wires from the fuel pressure transmitter box are routed through the hole in the A/C duct. Actually, they are already attached to the fuel gauge, so they are pushed through the hole and run to the box. Do the same thing with you nitrous pressure hose (if you didn't already push it through). I put a gauge connector in the -4AN line from the bottle, right at the solenoids. I put a tee in the gauge connector, then the purge valve went on one branch of the tee, and the -3AN connector for the fuel pressure hose went in the other branch. I then used two -3AN, 36" hoses for the gauge connection.

Attach one hose to the nitrous pressure gauge with the right connector for the 1/8" NPT on the gauge. Push the hose through the hole in the A/C duct and route it over to the grommet behind the computer. Push the gauge into the dash, straight, because it’s done. Connect another -3AN hose near the solenoids, and run it toward the computer. I have all the wires and hoses under the cowl tied in a bundle, and then use cable anchors on the bottom of the cowl, with cable ties to pull the whole mess up to the cowl and out of the way.

Join the two hoses with a -3AN union. The reason I used the union was mainly because I already had the two hoses. But this would also allow you to include at that point, an under hood nitrous pressure gauge and a mech. fuel pressure gauge....not essential, but it looks cool.

Hope this helps. I still use my A/C on really hot or humid days, and it works fine with only one center vent. Ohhh.....before you put the gauges in the openings, get a chunk of foam rubber and push it into the A/C vent so that you don't get too much cold air on the gauges, or blowing out the hole you made for the wires. I will probably think of more hints, but this is it for starters.

regards,

Fred