[twobjshelbys]

Do you have the faux 8-stack?

I had a Roush 427IR (Fuel injected 8-stack) with the Accel system mentioned and it took a year, shipping the car back to Roush, and then spending another 2K with a tuner in Fort Collins. The tune that Roush put on the system was not complete. It was firstly done on a Mustang with real mufflers (and back pressure). But it was not completely finished in that they never populated the altitude compensation table. I found a tuner that was trained at Accel on the system and tuned it on a dnyo and then did a 10K+' refinement on the altitude table and I was happy. I offered that tune back to Roush for my expenses but they never did anything.

If you have the faux 8-stack there is a small issue with the blending of the tables. As the throttle bodies open towards WOT, the air flow becomes straight in and doesn't get any turbulence as a result of flowing past the throttle flap. The result is that there is an incomplete air/fuel mixture and the engine starts to run rich. At that point in the throttle the FI system needs to lean out a little and then progress up again... This was part of the problem with the Accel but I imagine it happens with any of them, and this effect will really confuse self-learning systems...

That said, if you have a FAST system how old is the engine? Might it still be under warranty???