aftermarket EFI tech

I just bought the EZ-EFI and I’m still waiting for delivery. I have a 455 Pontiac. For the last couple of days, I’ve been reading up on it (should’ve done that first) and it doesn’t sound like it’s going to work for me. The only thing the salesman said is that it will work is

I recently bought a FiTech Go EFI fuel injection system for my big-block Chevelle. The engine is a 468ci big-block with a mild hydraulic roller cam, a TH400, a warmed-over converter, and 3.55:1 gears in the 12-bolt. I used to run an 850 Holley. It ran great but always was rich. We installed the system