Swapping a converter is a bunch of work. I wouldn't do that until I had checked all of the easy stuff. Compression check, firing order, double check timing, what do the plugs look like? How does it run at idle? What doe the vacuum gauge say? Good oil pressure? Have you replaced the FiTech with a known good carb to see how it runs? There are at least 100 things you should check on before you try a different converter.
Timing is good,oil pressure is great. Had a holley 850 on it before fuel injection went on was a pooch of the line then as well. Will smoke the tires if i tap the brakes, but even then seems like it should being climbing up on the rpms way faster
