superloaf

My car makes a turbo-whooshing-blow off valve sounding noise but only on boost. It didn't used to do this but started a few months ago. I just finished a big oil pan gasket job and found a cracked downpipe and cracked crossover to wastegate tube, both of which were replaced. I expected the noise to be gone but lo and behold, it continues. I should add that I have a B&B cat back which has become quite loud and the whooshing sound can be heard over the exhaust so it is very noticeable and annoying. It really sounds like an aftermarket blow off valve but as I've said, it only happens on boost and not accelerator lift off so I didn't think the blow off valve was responsible but I guess if it's stuck open maybe it could maybe cause this???

So any ideas? Would a bad blow off valve cause this? Anything else to look for?

Car is an '86 with 170k miles and original K26/6 turbo running 15psi.

superloaf

Doh, found the problem. It's what I thought was a missing exhaust manifold nut and stud but now I find the stud is broken inside the head. Arrrggg, is it possible to drill out with the head still on the car? Not much room in there but maybe with a right angle drill....? Which i don't have of course.

The other bolt/stud had come loose so I tightened that one and it's much better but still blowing out under higher boost; before it whooshed at any boost. I might try removing the other stud and sliding a new gasket in the opening which sounds fun but I don't think getting that broken stud out will be very soon!

Oh, and the car is much faster now especially at higher boost when at low revs in a higher gear which makes sense. I wasn't sure much power was being lost as it was still able to make 15psi but just making it that much quicker now and I can feel it.

Anyways, at least it's a bit better.....