hey guys,, been doing a lot of checking and buying for my 2001 29Scarab, my engines will be 383's , vortec heads with mild match-port ,, cam is 495int-509exh , EMI manifolds with stainless risers,, bought a Holley EFI Intake Manifold 9901-107,,, does anyone know if they actually flow better than stock? rpm range is 2000-7000,, ports are smaller than stock and injector boss protrudes into the runner,, my engines will be 383's , vortec heads with mild match-port cam is 495int-509exh , EMI manifolds with stainless risers

The Holley is a single plane and may not perform better than stock especially with your build. A good dual plane air gap is the way to go.

The factory EFI intake doesn't flow very well and becomes a big restriction at anything over 350-375hp. The Holley intake will flow significantly better. They generally leave the port opening a little on the small side so you can match it to your head.