Misfire at cruise, popping/afterfire at 3000RPM

halifaxhops said
If they are not cut frm the pick up plate they are right.

They’re not cut, so I think I’ll leave them as is.

512Stroker said
What plug wires are you using? Im sure you have checked the firing order correct? Cap and rotor?
Just spit balling, this has to be something basic.

I’ve got new Taylor 8mm wires. I don’t remember if I mentioned in this thread or not, but I found one of the porcelain boots cracked, along with the porcelain on one of the plugs cracked. Fixed that and it solved the misfire at cruise.

I’ve double and triple checked the firing order, made sure the wires are parallel and separated, confirmed correct wiring of the coil. One thing I haven’t done is checked voltage.

The biggest improvement was when I had a valve job done and replaced all the springs and valve seals. That changed the RPM when this is happening from 2800 to a little over 3400 (if I remember correctly?). So that would make me think this is mechanical and not ignition related, or maybe there are several problems going on here.