HELP!! need experts advice on 440 trouble.

Hey all FABO members.
I would have posted this under an "Engine" forum but I see every forum topic but engine? Anyhoo, read on and share your years of wisdom.

I just got this motor together, the short block was balanced, decked to zero and blueprinted, the RPM heads are off the old motor and worked fine on it, the cam is hotter than what was in the old motor, its a solid lifter Lunati with more lift but not crazy (.566/.586) and 280/288 duration.

Everything torqued down good, gaskets were better than average..it went together great.

Now, ever since it first started up I have this annoying noise coming from the passenger side that sounds like a header gasket leak...I have switched out the gasket twice and filed the flanges flat. I asked a friend for advice and he said maybe I had a burnt exhaust valve because it does sound like an exhaust leak so we compression tested that side of the engine:

cyl.
2: 160 psi
4: 155 psi
6: 160 psi
8: 160 psi

I don't think the 5 psi difference would indicate a valve problem but maybe you all know different. Is there anything else that can make a sound like an exhaust leak...it almost sounds intermittent but then again the cam is rough...bad plug or plug wire? maybe the cylinder is going dead now and again?

The plugs are all new but the number 4 plug was especially clean, like hardly any carbon on it at all.

Any thoughts would be great before I dig into pulling the head...which is essentially like pulling the motor when its a 440 tucked into my Dart with headers. If the compression numbers look ok to you all, can anyone say for sure that the valves and heads are not the issue here?

Thanks,

Greg in SC