I've seen a lot of hot-rod guys with seriously modified engines use Megasquirt. I've never used it myself so I can't give reviews on it, but from what I hear it's good stuff. Keep in mind most of these guys' engines have aftermarket cams, upgraded intakes and possibly heads, most of the emissions hardware gone, oversized injectors, and who knows what else. Some even run forced induction or nitrous oxide. Go to the message board at
www.thirdgen.org and check out the subforum
"DFI and ECM." It's a Camaro-specific site but there's a lot of good info there on EFI tuning in general, and a bunch of guys using Megasquirt that can help you if you run into problems. That site gets a lot of traffic so use the search button to find what you need. They don't like it when people ask questions that have already been answered a dozen times.