Carb experts Please help

Power valve. Are you running an automatic transmission? Check your vacuum reading in gear at idle, divide that in half and that's the power valve you should be running. With a manual trans, just check your vacuum at idle and divide that in half.

Check your float level and make sure you don't have a bunch of rust holding the float needle open. This can cause your float level to creep up at idle.

Fuel pressure. 6-7 lbs. is fine with a Holley. Rust can cause a fuel pressure regulator to hang too.

QF carbs all have a check valve to prevent a backfire from blowing the power valve, so I doubt that's it.

Make sure TDC is truly TDC as marked on your harmonic balancer, you might not be running as much initial timing as you think.

How much compression are you running? That's a pretty big cam to be running stock pistons in. The quoted 10:1 CR, once truly measured is usually quite a bit lower.