What is your timing set at and what is the octane rating of the fuel you are using? You may be on the verge of detonation when cyl's are cool, but as engine cyl temps rise, you have that additional heat to push you over the edge to detonation. Also could you be running lean?
Cleaning the MAF, IAT and ECT is where most folks start (the MAF being clean is super critical on 94-95's). Clocking the MAF if you have a CAI can help. Backing down timing or adding octane is common (or both).
Does it ping when really standing-on-it or is it under light throttle (that's a load-based processor question there)? AODE or T5? If the former, is the converter locked when it pings?