Steve,
I know you said you changed the power valves but sometimes the power valves are not the right size for your engine. You need to check how much vacuum you are pulling at idle. If it is say..12
lbs then you need a power valve thats a 6.5. You can find out which part number power valve you need by calling the Holly 800 number or go to their site. You can generally tell if it is a power valve thats bad by the smell of gas all the time while you're driving.
I hope this helps...
Hersh
