Note that the FAST EZ EFI 2.0 and XFI systems are different. I have the FAST EZ EFI 2.0 system on my 1970 Road Runner with a stock 383 and 4 speed. I also have the FAST distributor.
After I restored the car and got everything working, I drove it 5,800 miles across country with the FAST system.
To HIGHLY summarize my experience, I had a lot of trouble getting my system to run OK. The problem turned out to be a bad ECU, but the FAST tech support was very poor, constantly blaming the issue on me until I forced them to admit that I had an early unit that had issues. They then sent me (and charged me for it) a remanufactured ECU that instantly worked. They even screwed up and didn't properly return my funds when I send the faulty one back.
Once I got it running, it was trouble free for 5,800 miles, working well at sea level and 14,000 feet at the top of pikes peak.
So bottom line, tech support sucks, system has been good once I got it running.
Want the details?
My Restoration thread:
http://www.forbbodiesonly.com/moparforum/showthread.php?65096-Hawk-Rod-The-Restoration
A thread when I was REALLY PISSED at FAST:
http://www.forbbodiesonly.com/moparforum/showthread.php?96089-I-ve-Had-It-With-FAST-EZ-EFI
My trip across country:
http://www.forbbodiesonly.com/mopar...7639-Hawk-s-Cross-Country-70-Road-Runner-Trip
Good luck whatever you decide