@jffr posted:What kind of intake manifold are you using on your engine? An EFI throttle body system should work good on a Pantera . I know of a couple of Panteras here in Arizona that run very well with them. You are quite possibly pushing the limit of a throttle body system with the horsepower that you are making. I have been using the FAST XFI 2.05 sequential port fuel injection system for 12 years and haven't had any problems with it. I have a CHI 3V single plane air gap intake manifold and the engine is making about 550 horsepower at the flywheel. I have two O2 sensors that are on each exhaust pipes right next to the header collector. One O2 sensor is for the in dash O2 gauge and the other runs the EFI. Although this FAST system is quite old and has not been updated in at least ten years, it performs like a modern fuel injected vehicle. It does have a great deal more tunability than the throttle body systems that I have seen, which could be why I have not had any trouble with it. It also may have helped to have the engine tuned on a dyno by someone that was an expert in EFI systems. I am certainly not and know just enough about EFI to be dangerous!
@jffr, I'm using a Victor Jr. intake. My FAST EZ TBI had 4 injectors. 1 O2 sensor (as you know, there's basically only 1 spot per side to accomplish upward angle and easy access, so it was basically where yours are). 636 bhp was within the limit for the FAST EZ per its manual (we set the fuel pressure regulator accordingly by their manual). I also called FAST (Edelbrock) several times in the process and was given some interesting suggestions, some of which were contrary to the manual and the logical startup wizard and TPS reset procedure, etc., but nothing was really solving it, and it was out of warranty by the time we put it in the car, and I had already had "successful" Pantera FAST users (not EZ versions) spend considerable time with it, also unsuccessfully if for no other reason than fouled O2 sensor, so after a few more resets on new O2 and plugs, I bailed on it. Tuning was initially done on a dyno, but that was of course without my exhaust, etc., and that shop was over 5 hours from me at the time.