power loss/loundess problem came back

[GTIrl]

it was going really well after rolling road/ timing/ fiddling and exhaust re -stuffing. thought the problem was fixed, but today i started it up and it sounded loud and felt down on power again. if you guys have any ideas id be very grateful of a suggestion or hearing of anyone else's experience?

[GTIrl]

another thing...could it be my knock sensor? what would a knackered or intermittently knackered knock sensor result in? car was running smoothly but now its back to sounding like the timing is out (tho it definitley isnt)its loud and i think it may be pinking, also alot more backpop. so sad, it was fun while it lasted..

[VeeDubGTI16v]

loud like an exhaust blowing? id check all the joins in the exhaust if its just been played with