Nothing wrong with the performer RPM
We ran 12.07 @ 119 mph with a .030 over 400 with stock unported heads with a factory ram air 3 cam and a 850 Holley
Its all in the tuning
If you really want to go fast ditch the iron intake.
Low RPM power and cfm is nothing but internet mythology
A Modern 5.3 LS has better heads than any aftermarket pontiac heads and a tiny 5.3L can move a 5000 lb truck pretty [censored] good. Most likely blow the doors off any 3500 lb Firebird with a 326 or 350
prove me wrong