High RPM Backfire when fully warmed

SRT_DSTRHOLC said
how is it not true and then good for one setup? do you know what his build is? how would it be not true if we don't know the setup? We are looking for examples that lead to his issue. For a max power and efficent engine, the timing could be better...

I will add that timing is NOT the main issue right now, but it could be better. The issue looks like fuel, that plug looks like it could be practically new or not idling much.

I’ve built a lot of magnums. That’s how. I actually currently have almost the exact same engine as the OP in my D100. On top of that I’ve tuned everything from 100hp NA 4 cylinders in roundy round cars to 1500hp turbo LS drag and drive stuff. I have many hours tuning and looking at plugs on engine dynos. This ain’t my first rodeo.