Check to see if your downpipe is rattling against your trans crossmember, I have had that problem on mine every time I have to drop the downpipe. I usually end up just using a prybar to pull the dp away from the crossmember while I tighten the bolt that holds the bracket on the dp.

 

looks like the header is leaking. but doubt that it's causing your noises that you're hearing but after putting back the stock header did the sound go away?

Jon

 

yep. apparantly it was the header..... no matter how hard i tried to make the sound come back it would not.... some really wierd stuff yet it makes sense in a way. the sound would only occur if it was hot under a heavy load, i guess the leak must have intensified when it was hot.... i dunno im just happy the sound is gone and it wasnt a drivetrain problem. i cant believe how much time and money ive wasted because of this leak

:RockOn - not mine:


for search purposes:

gruppe-s header
knocking under acceleration
grinding metal sound
cracked header

 

nice. guess you'll have to have vakamon weld your header instead of those connection sleeves since those are leaking

Jon