I have a boost leak on my 93 mr2 turbo, but I can't seem to find it. I just replaced my timing belt and such, and I also installed a new intercooler and piping. All of the couplers are on the piping correctly, and the t-bolt clamps are tight, but it's still leaking under boost. It's extremely loud when I boost, almost sounds like a waterfall. And when I press in on the clutch, it sounds like I have a HKS SSQV, when in reality, I still have the stock blow off valve that dumps back into the intake. It will boost some, but when the turbo builds any amount of pressure, it's really loud. This happened once before when one of my couplers wasn't tightened down, but everything is in place. Any thoughts?

headgasket? vac leak?

Intake manifold gasket? Check it. If you want to save troubleshooting. there a kit for testing boost leaks, or you can make your own. My tuner took a piece of aluminum pipe and welded a cap and a fitting to one end, so he pushes compressed air into the system and therefore can detect any boost leaks.

possibly that is a coupler, it don't show when you are not boosting and it opens and leak air on boost, check them all having them in your hands.
very hard to find when they are on the piping, my experience tell.

you replaced the timing belt...are you sure the timing is correct?

I unhooked a vacuum line on the intake manifold and blew air threw it, and it turns out it was leaking at one of the couplers. I fixed that and now it runs fine.