my 01 has about 138k on it. it pings very bad under load. occasionally it throws a p0420. other times it throws a camshaft reset valve code. I need to get this up to par. What typically causes pinging on these? should I have to run premium? Im thinking the cat could be clogged.

 

P0420 is telling you the ECU compared the two O2 sensors and the difference is too high. Typical causes are misfires, vacuum or intake air leaks, fuel pressure issues or a bad cat. Pinging means ignition from compression not spark. Could be a lean condition making the engine run hot. Premium may help but isn't required in these cars, nor does it help you find the root cause. I'd start by looking for vacuum leaks, pull the plugs to check for color, then measure your fuel pressure to see if its normal or wanders. Finally you can try pulling out the front O2 sensor to see if it runs better by releasing some back pressure from thecat.

 

OK, I am getting a 644a code. I checked the timing marks and they all seem to line up. Is there something else I can check? Is it possible the solenoid is bad for the variable timing? The resistance checks out OK.