98 OBW 2.5L Phase I Ping

I have a dilemma that I can’t figure out. If it has been posted somewhere else please redirect me to the postings.

I have a rebuilt 2.5L Phase I engine in my 98 OBW. CCR Inc did a great job on the rebuild. Before I found out that I had crankwalk on my old engine I took the OBW to a couple of shops to see if they could get it running right. Come to find out one of the shops played with the TPS on the throttle body. Now here’s the problem. I live at altitude, 7000ft., and when I pull a hill I can here some pinging. When I go down off the mountain for meetings and pull away from a stop sign the pinging is almost unbearable. I’ll also get engine code of 301,302,303, and 304 (engine misfire). When I return to altitude, after a few days the CEL goes out and no more codes. Could this be a TPS problem? Altitude sensor problem. Timing problem. Any insights would be helpful.

Thanks,

Mike