Well, the boost gauge I'm selling is mechanical, so all it needs is a sensing line (i.e. 1/8" rigid plastic tubing), from an appropriate vacuum/pressure source under the hood, routed through the firewall grommet, to the gauge.
I like to remove the OEM fittings and tubing between the black, metal harness coming off the doghouse and the MAP sensor on the RH fender, put them away for posterity and run a new HELP vacuum fitting (1/8" X 7/32") and new 1/8" tubing to the gauge. This renders the OEM LED boost gauge useless, one LED will light at all times, but who needs it anyway when you have an aftermarket gauge - it's inaccurate and of insufficient range, which is why you bought the aftermarket gauge in the first place.
Be very careful not to kink the tubing. Make sure the ends of the tubing are open - I use an awl to open them if necessary, but I suppose a small nail would do just as well.
Check to make sure the fittings on the back of the gauge are tight, but not overly so or you'll ruin the gauge or ferrule. Use teflon tape or some other thread sealer where appropriate, but don't overdo it.
Zip tie your connections at the harness to be sure they won't come off.
The gauge has a light, which of course takes 12V and ground. If you don't care to light the gauge, you don't even need to do that. Not being a night racer... Some guys like to power the light off the fuse box dash lights, so that the gauge can be dimmed. There's a good chassis ground under the dash to the left of the steering column - I think it uses a 10mm screw - you'll see other wires grounded on it.
That's really about it for the boost gauge.
