Are your flow numbers with the Edelbrock valve Job? The on reason I ask is it can cause you to lose low lift flow.

Some flow numbers on a RPM Magnum I just ported

Edelbrock Performer RPM Magnum

.100 74cfm .100 62cfm
.200 151cfm .100 118cfm
.300 221cfm .300 160cfm
.400 263cfm .400 196cfm
.500 288cfm .500 217cfm
.600 294cfm .600 220cfm
.700 297cfm .700 236cfm

Intake Valve 2.02 Exhaust Valve 1.60
( Exh. Flow Tested with a Flow Pipe)
*Flow tested at 28 inches