The Weirdest Vacuum leak
 

Hi, So I have a 95 with a BRP SC with an intercooler and MS2PNP ECU. Currently, my car starts up fine, but when I start it when it is warm the idle sets at 900 then it creeps up to about 1300. You are probably thinking that it is a vacuum leak which is what I thought but my boost gauge is reading 20HG at idle and it's hooked into the intake mani. It drops only when I give the car gas too.

So seems not to be a vacuum leak then? So then I thought the IAC was bad or stuck open, Luckily my IAC is remotely mounted so I tried unplugging and blocking the hoses that connect it to the TB and the Intake tube. No luck so it seems not to be the IAC. I also have sprayed the absolute crap out of any possible v leak areas, like the dummy TB gasket, injectors, vacuum hoses nothing. The bypass valve is functioning too and it opens when given throttle.

Honestly, I am super lost. Are there any tips for fixing or finding the issue? I can post my tune and logs but I don't see why I would need to.

You can try a smoke test, I'd also check the connection at your boost gauge. It's also possible your throttle body is gunked up, I know my SC was pretty filthy after 10k miles.

The other thing to check is your throttle cable, if it's sticking it could cause a high idle, the MS could be lowering you down as you drop to neutral and then it creeps back up.

The smoke test is a good idea. Now to find a way to do it