I have a 2004 a4 and I want to install a boost gauge. Can anyone help?
There are 2 wires and 1 plug in the center, it looks like a hose would
hook up to it. If I had the instructions for the gauge I wouldn't
need help. Plus I don't have a manual for the wiring diagram cause
I can't find any local auto store that sells it. Can anyone help
please?

Thanks
A.J.

 

I suggest you PM robbie_boy who made and installed his own boost gauge. Someday we will post up a detailed DIY on this subject.

 

you need to find the hose that runs from the inlet manifold to the top of the DV cut hose then insert a tee piece.
with the spare nipple on the tee attach hose and feed into the cockpit to the dashboard,that end of the hose goes onto the (plug)nipple on the back of the boost guage
as for the electrics one wire will be a ground wire the other will be a switched live,
the ground wire can either go any where on the chassis/piggy back off another ground wire or direct to the battery,the switched live will will either go to the ignition switch/piggy back of dash lights or the head lights.
hope this was of any use to you