I have a Fitech, on a 410 LA engine with a procharger, had a few learning issues, but it works very well after I got the bugs out.
Someone mentioned over 50 psi fuel pressure, nope, mine did not like it at all, it is more like 40 psi. And the unit has a pressure regulator built into it, but it does not have the capacity to control a large volume and pressure fuel pump. All the sensors and replaceable parts in the Fitech are over the counter available parts at any parts store. The pressure regulator is from a 1.8 Volkswagen system. If you have to much fuel pressure, the drivers in the ECU will get hot and shut down. The higher the fuel pressure the more amperage it takes to lift the injector off it's seat. Took me a while to figure that one out. Second issue I had was the Fitech control of ignition timing, use a MSD distributor, I tried a cheap Ebay MSD copy and it ran the engine just fine on a carb, but would not handle the Fitech. Both distributors use a magnetic pickup, but believe it or not the MSD copy makes more voltage than the real MSD and the Fitech did not like it over about 4,000 rpm. Got scope patterns to prove it. Others may have had better luck with other types of distributors, but that was my experience.
Fitech also sometimes has EMI issues. I simply used some of the cheap fake wire braid sleeves to slide over the harness, and that fixed that. Nice thing is it will set a code if that is the problem. https://www.amazon.com/Universal-Stainless-Steel-Braided-Dress-Up/dp/B01MYYHDCF
Just solder a ground wire to the sleeve and ground.
The handheld unit that comes with the Fitech is like a scan tool, it even records OBD style trouble codes, just like a modern car. A very powerful tool. My only trouble was with Fitech giving me good info on the parameters that set those codes. I just think the Tech guys on the phone were not trained well in the system. For example when I wanted to send scope patterns for them to evaluate, and or asked for what voltage values certain components worked with to use a scope, they really did not understand what I was talking about. Often they relayed my requests to an engineer, and I never really got a good answer. I will have to say many times I get similar issues with most companies technical phone contacts.