Here's a challenge.. Please help!!

I am the owner of an 04a4 gto with 63k. I've been having a knocking problem for a while now and am looking for some advice. I am an experienced mechanic so i do know what im talking about. but this one has me stumped. The dull woodlike knocking sound is very noticable from in the cabin, but not outside. And It does change speed slightly with rpms, until about 25k when it either goes away or cant be heard anymore. It only starts once the motor is warmed up and doesnt stop untill i shut off the car. Dont think its a valvetrain issue, or itd be more noticable outside the car and be especially loud outside the car and at all temps. Or an exhaust rattle as i run a full performance exhaust and there's plenty of clearance all around the pipes. driveshaft? tranny? motor mount? Any advice is appriciated!

Nobody has anything? I thought one of the purposes of this forum was exactly this

The way you descirbe it as a "dull woodlike knocking" tells me it has to be the exhaust as the undercoating of the vehicle insulates the metal on metal contact to create this type of sound. Or perhaps there a problem with one of the hangers and the system is "bouncing" in the hanger's eye?

Have you driven her hard into the corners? These cars had 235's on them when produced down under and pontiac put 245's on them over here without changing the alignment specs leading to a front strut rub.

Once your tires warm up the could the interior side wall begin to bulge???

I don't know I'm strugging here...

The only weak link in the value train are the push rods - lots guys replace the OEM rods a higher quality push rod.