EFI question

cu440da pretty much nailed it. I have a Megasquirt in my 5.7 and it's been pretty nice. It's very flexible, so you can start with just the basics and gradually add features as you get used to it. It's also incredibly capable, but requires a little more knowledge to get it to work. You can just about make it do anything, but you might have to build a circuit yourself to interface with the component you want.

I debated a FAST system as well, but ended up finding my Megasquirt for a good deal first. The FAST setup can actually run a port injected system as well as a throttle body injected setup. They don't advertise the port setup much, but it's basically the computer and a wiring harness. You'd still need a throttle body to replace the factory drive by wire setup, but you wouldn't have to change manifolds for a throttle body injector setup. It's also more of a closed system that only auto tunes as I understand it. That means you can still change engine parts and relearn, but you can't necessarily manually change something in the tune (I might be wrong on this).

The Holley I have no experience with, but I think is similar to a Megasquirt setup. I think it's a little more like a plug and play setup in that it probably has several canned settings that you can pick to match existing engine parts, but I've really never looked into it much. Frankly, Megasquirt setups have come a very long way and they have a nice plug and play 3G Hemi setup and some nice weather sealed units that can be mounted in the engine bays now, so I'm not sure where the Holley really fits in the equation other than name brand.