Clicking

Hi, 91 XJ 4.0 HO, 8" skyjacker RR kit. Ahh, I have a weird question. What do you think it is when you hear a clicking noise coming from the engine when it is running? It gets progressivly faster when I accelerate. My oil is full, so I don't believe it is that, and I get good pressure and such. Could it be a bad valve or pushrod? Is there anyway I could find out before I have to tear it all apart? Sounds like its comin from cylinder 6.

Exhaust leaks click with RPM. Well, more of a "tick" actually. Rods knock and pistons slap. Check engine light on?

Does a 91 have a knock sensor? If so, a bad one would allow knocking.