i have been having some problems with my car pulling the timing shortly after timing it. i got a sacanner and saw the car is sensing knock, but dont hear anything out of the ordinary. i do have some pretty bad exhaust leaks at the hedders (bolts keep backing out) and my y-pipe hits the subframe connector, however i have a piece of rubber hose in between that and it wasnt a problem long ago when i had the car tuned

i have pulled one valve cover off just to check that nothing was out of place. all rockers seemed tight enough, no pushrods out of place, and the rockers couldnt be hitting the valve covers because they are 1.5's with tall valve covers, and i never had that problem before.

does anyone have any ideas of things i could check? i have no idea how to tell what the knock sensor is picking up

more info:
timing starts getting pulled around 3000 rpm
92 camaro speed density
350 gmpp crate motor with tune
ran perfect for a few months after a tune, then had problems and couldnt drive it hard, therefore didnt know about the timing being pulled
have timed it at least twice and tiing is pulled the next day, however runs great on trial runs after setting timing


any help would be appreciated, maybe i can learn something here too