Once again, I posted this for you back in September of 2001:
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My 86 951 had a terrible rattle that we couldn't find either.
1st) Thought the O2 sensor was rattling in the exhaust - that was fine. Still rattled.
2nd) Thought the double-walled downpipe had separated - replaced it with 3" SS downpipe and cat bypass from fabspeed. Still rattled.
3rd) Checked the turbo, the heatshields, and anything else that might be loose. Still rattled.
4th) Replace the small (8" long) pipe that comes right off the turbo and the downpipe bolts to. THAT WAS IT!! That pipe is double-walled also and had split on the inside where the inner pipe is welded at the flange on the turbo side.
Smooth as silk now and no noises.
I have the original part still - I will snap some shots tonight and post them here of the split on the inner portion of the pipe.
BAD NEWS: THIS PART IS NOWHERE TO BE FOUND IN THE USA. I HAD TO ORDER FROM PORSCHE AND IT CAME FROM GERMANY AND TOOK ABOUT 10 DAYS. $400 FOR THE PART.
I would NOT replace it with a used one either. You are just asking for problems. This pipe is subjected to some serious temps and the expansion and contraction takes it's toll. Not easy to get to either.
Hope this helps.
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This is from this post:
http://forums.pelicanparts.com/showthread.php?threadid=14456&highlight=noise
The part is not $1000, that is B.S., I paid about $400 for it from a Porsche Dealer.
Good Luck.
-g