[CarlC]

Dave hit the nail squarely on the head. Thanks for putting it so eloquently.

It's been a great experience working with Dave and Mark on some very challenging builds. The large returnless fuel systems can be tough to make work well at low fuel demand. Like tuning, the WOT is easy, it's the idle, cruise, cold start, etc. that is tough. The bigger the pump, the harder it is to control. We have customers that are running three (yes three) TI450lph pumps on a fully returnless PWM system.

Another thing to consider is that the GM FSCM does need to be married to the ECM via a TECH2. Hence, if the FSCM need so to be replaced the car will need to go to the dealer to have the work done. The VaporWorx controller is stand alone.

Oh, and for those that might consider adapting the LS9 fuel pump and controller that Dave describes, the last time I checked it was $3k+ for parts. Replacing the injector is a much better option.

I believe we may see similar FSCM controller limited conditions on LT1/4 crate engines. Time will tell where the limits of the controller are, but GM is not one to put an excessive amount of overcapacity into such a system, and we're working with near 1000hp builds already.