Misfire at cruise, popping/afterfire at 3000RPM

Mattax said

So we still have little idea what the timing looks like, but now know it was 41*BTDC at 2800 rpm.
Yes that could damage at full throttle.
Whether it did cause mechanical damage or not, definately want to avoid going close to full power with too much timing lead.

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So it was likely at 45*BTDC when my initial was at 20, am I following here? And with the vacuum advance connected, likely even higher (assuming the vac advance is functioning)? I have an FBO limiter plate kicking around, thought about installing that. BUT, I think I'd rather troubleshoot and find the actual problem first.

I'm definitely worried about causing damage, so when it starts to stumble and act up, I immediately let off the throttle.