[Soundkillr]

I have a 428fe with a holley 850 double pumper. Im currently rebuilding it, and while its apart I would love jetting recommendations for the top end. Car runs awesome until 4500 where it just stops making power. Ive got edlebrock rpm heads and intake...but unsure of cam...
The car has two power valves. Both 6 both blown. I need new power valves and was told to try 6.5 as I have about 15 or 16 inches of vacuum. I also have 80 idle jets all the way around...and was told to try 83 in the rear bowl. Car is supposed to have 550hp.
Runs great till about 4500 and runs out of power. Any suggestions?
This is a non vacuum advance set up. Ive seen people do a power valve delete in the rear bowl...but im unsure what that would gain me