With two sets of head gaskets and no change in the noise prob not the issue. I would pull the MAF pipe and check the turbo for play and/or wheel to housing contact.
Another thing you can do IF it gets that far, is to pressurize the intake. Let me know if you go that route as I have made an aluminum plug with an air fitting that clamps in the charge air piping for this and I'm in League City. On mine I put it where the MAF goes and went to 20psi located several leaks this way. You do have to pull the rockers though.
I wouldn't think it was head gaskets, the Rjc bulletproof kit was put on, heat cycled and retorqued by century. Need to get it up to 20 psi with the pressure test. I saw a video where the tail pipes block off the tail pipes and pressurize the whole thing from the turbo back. The turbo had less than 2000 miles on it. But it might have taken a beaten when it overboosted.
There are so many things that can make crazy noises on a boosted car. On mine the upper to lower plenum gasket was leaking directly under the throttle body only under boost when I got it. That's what let to the pressure testing. Found the upper to lower intake bolts were just loose. It only made a noise above 18psi and it whistled super loud! Drove me crazy until I found it.
Really need a shop that will work on Buicks on this side of town, also on the south side of houston , near league city. I do not have time to mess with my own car right now. Much less my dad's car... If you know of one , let me know.
