I have had a FAST xfi computer in a new 427 sbc motor in my '76 for about 15-16 months now. It has never run right and I have spent almost $6k trying to trouble shoot this system. I previously had an older edelbrock system on this car that ran flawlessly for 14 years or so.
427 with dart little M block etc.
10.4:1 cr
comp cams solid roller .670/.670 lift 250/258 dur, with stud girdles etc.
AFR elim 210 heads
1 7/8 hooker sidepipes with spiral baffles
MSD 6A with comp cams dual sync distributor

I have to say that FAST refuses to honor their warrantee, so watch out for that too. Here are the problems I had.
1. Had a bad dual sync sensor. Put an MSD crank trigger on it
2. Motor was leaning out at 5,000 rpm so bought a new TB, ported intake, adjustable fpr and injectors for roughly $2500
3. Motor still flatlined with hp at 5,000 rpm even though tq peak was roughly 4700 rpm, so spent $500 on new springs. This did nothing
4. Sequential mode never ran right and peaked at 350 rwhp.
5. alpha N mode peaked at around 390 rwhp with the above flatline issue at around 5,000 rpm
6. Have had all kinds of TPS problems with it jumping around inconsistently.
7. The computer would not retain the tps values despite multiple reflashes and resets.

Warrantee
1. After The efi tech and I both had worked on this thing for almost a year, I sent the computer and O2 sensor into FAST to test it, worried that they wouldn't honor my problem outside of the year warrantee.
-They said the computer was fine, but didn't test the thing in sequential or even send me a read out of any sort.
-they said my data logs showed the tune was fine
-they said the O2 sensor was bad but that it was a 'high wear' item and they wouldn't cover it in their warrantee, but they would give me a good deal on a new one at cost for $280.
2. So despite being pissed, I bought the new O2 sensor, put it in and this sensor showed up almost immediately as an error 16 and quit working in closed loop mode.
3. Now they are demanding to send the computer and O2 sensor in again before they will do anything. All they are going to do is claim it is again a high wear item anyway, so what is the point?

This system seems to be very unstable. Problems flashing the computer etc. I think it has a bad computer and have maintained it all along, but FAST does nothing. Remember I had efi on this car for 14 years without a single problem.

Anyway, I'm not too happy and wanted to know if anyone had any similar such experiences or any suggestions.

 

With such a combo and knowledge it sounds strange you did not run dynos to setup your ECM. any reasons ?

Anyhow, I do not know the fast reliability so.....good luck !

 

I stay away from any CompCam products! I ran into a similar warranty problem when I had purchased a set of of Pro-Magnum 1.6 ratio rocker arms. My mechanic installed them and when he went on a test run bent a valve. The problem was that they included one big block 1.7 ratio rocker arm. CompCams wouldn't cover the damage caused! All they wanted to do was give me some credit towards more parts which I did not need!

Yes, mechanic should have noticed when installing but when you buy new rockers in a set of 16 from a supposedly reputable vendor you expect them all to match.

So since then I won't buy / install ANY CompCam products!

I'm not sure if it's too late or if you paid with a credit card but, I would contact your credit card company with the history of the issues and see if they can do anything for you. I did this once for fiberglass body parts on my '73 Duster and got results!

 

I have a hard time believing that if you just got a new sensor and it isn't working that they wouldn't warranty it. I think you should double check your wiring to make sure everything is wired correctly.

Teh dual sync is pretty crappy. its an accel dual sync they use and I had mine go on me with 100 km on it and left me stranded with a $300 flatbed charge.