Is the knocking only at a certain RPM. My car knocked LOUDLY at around 850-950rpm. Popped the hood, looked at the tensioner as I slowly revved the engine, sure enough, the tensioner was vibrating quite a bit. Replaced the damper on the tensioner and it took care of the problem. The tensioner now is as smooth as can be, and the knocking is gone. Not sure if it is the same set up on the 16v, but thought I would offer my fix.