Tuning problems
 

I'm facing tuning problems, most specifically pinging on my 1995 325i manual transmission with 115k.

I hear pinging under light acceleration in 1st-3rd. Under heavy acceleration, there is no pinging. I can floor it in a tall gear up a steep hill, and it is quiet and smooth. I don't have the check engine light, so no codes. I recently tested my knock sensors, and they seem fine. Plugs and wires are new. I recently installed re-manufactured head - so no carbon build up, and the noise was also there before the head repair too. I'm using premium gas, 92 octane.

Any suggestions?