Glow plugs....lol.


Get it up to full load where it's lean (the white porcelain)........the body of the plug which is still sooty from being too rich at low load........that's a hot spot for pre ignition.


But it's not just the plug.

If you shine a light down the hole.....it'll all be sooty.


How can it NOT be a bad tune?
A tune is a tune is a tune and it's NOT just about changing software parameters.

 

This is definitely one possibility. But was the tune done before the meth injection or after? And was the meth injection timing changed after the tune?

But this isn't a good sign since running too rich can wash the cylinder walls and cause excessive wear, especially with lean condition in the higher rpms. Engine won't last long before blowby start causing more problems that can kill the engine.