jetta, mk3 engine noise

I noticed some valve noise and upon inspection of my engine noticed the valve cover bolts were loose. I tighted them to spec and thought I had solved the problem. (To proud for my own good.) Didn't do the trick and its getting worse. Now my car sounds like a fork stuck in a blender. There is one more thing though.....it only does it when the engine is warm. There is oil pressure, it has fresh oil in it, no coolant has leaked into the oil, the plugs are new, and it rarely sees above 4000rpm's (just when I'm feeling froggy). The timing belt is original to the car and the clutch is on its last leg (if that helps any). I'm fresh out of ideas. Anybody got any?

Sorry

Should have mentioned that my car is a '97 GL with the 2.0L 8V and 5 spd manual tranny.