318 Running Rough / Backfiring

74Dart318 said
Fuel pressure jumps around between 5&7 psi

I'll have to pull the plugs

Backfire through exhaust

Popping, burnt exh valve...but backfire is loading up unburnt fuel with heat setting it off down the line.
What fuel pump are you using?
It is possible you run champion plugs and an insuator came lose, it is misfiring.