I have only experience with an EZ Efi and I wont get into the issues I had with FAST overall but what I will say is their stuff is not worth the price hike it has over a Megasquirt. I can get a plug and play MS3 for a little over 1/2 of what an XFI setup for a Gen III is and its all in one box to boot. Im gonna be my own tuner and learn how to do it so I can install the stuff on other cars as well. There is also a thread on another site about what a POS the EZ 2.0 is too.