[tahoerdr]

1) Unscrew 4ea T-20 torx to remove the lower DS kick panel (under steering wheel)
http://i8.photobucket.com/albums/a47...nIDDocs003.jpg
2) Unscrew 2ea Phillips head screws to remove the hood latch and loosen the panel. Pry it back, a white plastic clip will pop loose to allow the whole panel to be pulled back, but not completely removed.
3) Install the 90* OBD connector and run the wire up & behind the panel. I tried to run it outside of the panel but the angle of the cord wouldn’t allow it to get in past the panel to connect to the OBD port. This will make it a real pain to unplug the P3 OBD connector if you want to hook up a BT tool, etc.
http://i8.photobucket.com/albums/a47...nIDDocs006.jpg
4) With your head down in the foot well, look at the thick bundle of wiring going through the firewall. You’ll see a black “+” in the upper right of the rubber grommet, 2” from the wire bundle. Take a screw driver and poke through this hole 1”; you’re dislodging a plastic cap at the other side in order to run the boost line through this hole.
http://i8.photobucket.com/albums/a47...nIDDocs012.jpg
5) Pry the vent from the dash. It is secured with two metal guide posts . There’s not really anything to snap or break, just as long as you don’t pry only one end off at a time. I was able to loosen the right side first, backed it out 2”, then slid my fingers under/behind, moving toward the left. It took a bit of force but it got it without any damage done.
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6) Pop loose the arm at one end for the vent flow control flap.
http://i8.photobucket.com/albums/a47...nIDDocs009.jpg
7) Use a small flat head screw driver to pop loose the clips that hold the cowl (air supply pipe) to the vent frame. With cowl removed, you should be able to spread open the vent frame to remove the vent face, held in place by two small tabs on each end.
8) Drill a ~3/16” pilot hole in the side of the vent cowl in order to route the gauge wire out of the vent. It will be on the same side as the flap control arm. Then drill with a 1/2” and ream it out a bit more.
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9) Make sure the slats in the vent are oriented toward the driver, away from the gauge; this should help direct air flow out the remaining open side of the vent.
10) Feed the wire through the hole and carefully seat the gauge in the vent frame via the two metal tabs on the sides of the gauge. Be careful, they bend easily.
11) Reattach the flap control arm once you’ve played with both levers, ensuring that the “open” and “closed” indicator markings on the vent exterior coincide with what the flap is doing.
12) Feed the wire down to the foot well, then press the vent back into place.
13) Connect the black plastic box to the RJ-86 Ethernet cord coming from the gauge
14) Connect the black serial connector to the black box serial port
15) Connect the silver serial connector to the serial connector of the OBD cable.
16) UNDER THE HOOD: Remove the plastic 6”x6” cover over the brake lines on the driver side.
17) Unclip the two tabs holding the nearby rubber gutter in place and peel it back toward the rear of the car with one hand. With a flashlight, you’ll see a small black plastic rivet holding the gutter to the inner fender. I used a thin chisel to pry the plastic pin out and remove it.
http://i8.photobucket.com/albums/a47...nIDDocs015.jpg
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18) The gutter is attached at the firewall, simply pull it off the small black hexagonal post. You should be able to move the gutter around a bit now, don’t worry about removing the gutter completely.
19) You’ll see the wiring bundle that you saw in the foot well is protruding out just below the rubber gutter, and above it is a 1” diameter round plastic cap that has popped loose due to you punching that screwdriver through in step #4. Remove the plastic cap and fiber cap behind it, revealing the rubber “+”.
http://i8.photobucket.com/albums/a47...nIDDocs011.jpg
20) Drill a 3/16” hole through both caps and set aside.
21) Locate the 2 diverter valves on your charge pipe, just under the airbox on the driver side. Between the two valves is fiber-wrapped ¼” vacuum line that splits off from one line into both valves. Pull the single line off of the plastic “Y”. It was pretty tough for me, but eventually came loose.
http://i8.photobucket.com/albums/a47...nIDDocs010.jpg
22) Insert the white plastic barbed connector of the supplied vacuum line into this line you just disconnected, then the adjacent rubber coupler will connect to the “Y” going to the diverter valves.
23) Run the vacuum line to the hole in the firewall that you created, secure with zip ties. I ran it to the fender first, then along the fender and down to the hole.
24) Run the line through the caps that you drilled holes in, then snap the caps back into place.
25) BACK IN THE FOOT WELL: Pull the slack in the vacuum line through the firewall, cut all but 12” off if you plan on mounting the serial connectors right there.
26) Tidy up the wiring and vacuum lines with zip ties.
27) Start the car and check that it works.
28) Reinstall gutter, plastic cover, kick panel, and enjoy.

The gauge came with NO instructions at I couldn't find anything online. The website for the gauge says instructions are coming soon, hasn't been updated since May. I take no responsibility for this DIY causing you to break anything on your car or the gauge. Drilling the hole in the vent was the most questionable step. I'm not sure how else I'd route the wire.