Zero10

So, I have a problem. When I bought my car in NYC, it held 21psi of boost through most of the rev range, tapering off to well over 10 by redline (maybe 17?). Lately I haven't really gotten into it a lot, but recently, I started pushing it harder, and I get 21-22psi at 3300-3500RPM, which holds until about 4000RPM, where it starts tapering off. I have to shift before 5000RPM (maybe 4700-4800) to keep power, otherwise my boost will taper off to just below atmospheric by redline. It feels like I just run out of power by 5000RPM.

So, I'm trying to pin down the problem. I pulled the entire exhaust apart, and re-assembled, fixing a couple rattles in the process. I checked over the intake, and other than bad O-rings on the TB (which will be fixed soon), there are no big leaks. The ISV leaks a tiny bit, but I suppose they all do. It's not an intake/exhaust problem.

So, my next guess is wastegate. If I keep a close eye on the boost gauge, am I okay to disconnect (and clamp off) the line to the wastegate? Wouldn't this keep it closed? (or would it keep it open?.....)
I know it's spiked to 25psi or so without knock, so if I keep it shy of 20psi, I should be safe, right?

Any other suggestions on where I should start hunting?

It still has stock boost control. It's chipped, and has an aftermarket banjo bolt, as well as a shimmed wastegate.

Zero10

I should note. I am unable to find any exhaust leaks. I don't hear any exhaust leaks, and I can't find any sooty-looking areas on the exhaust. With how much oil I burn, I would imagine that I could see any leaks (I found one this way upon exhaust disassembly).


I said it was not an intake/exhaust problem, this is why I think so.

Chris Prack

Yes you can crimp the wastegate line and see if the boost increases. Just be smart about it.

Zero10

Okay, I'll actually disconnect it, since my line has been re-run it's actually easier for me, since I don't have anything very secure to pinch it off with, but I can plug it

We'll see what happens.