How much fuel is "a lot"? When I put the header on the 122, I forgot to reconnect the cold start injector line to the rail. When I cranked it, the pressure shot a nice line of fuel well past the fender. A pressure gauge will do wonders in determining if you have sufficient pressure. If not, the two obvious suspects are the FPR and the pump. If the pump kept the engine running in the old setup, your list of suspects diminishes substantially...

Pumping the go pedal "should" do absolutely nothing unless you're cranking. These cars aren't equipped with any sort of accelerator pump. I'm not sure if they are equipped with a "flood clear" function. That's a condition where, while cranking, anything past a certain throttle position actually stops firing the injectors, allowing the system to "dry" out.

Have you pulled a spark plug to see if you, in fact, have any fuel getting into the cylinders? That will narrow possibilities in a diagnosis as well.

Is it possible that you may have unwittingly knocked a wire loose and the D-jet system isn't getting any signal to fire the injectors. A scope is a great tool to determine if a signal is being sent to the injector. D-jet uses a trigger from the distributor to determine when to fire the injector(s)...not sure if they're sequential or batch fire, but that's not going to be a determining factor in this situation. We just need to be sure the injectors are actually firing...

Leaky injectors will allow fuel to drip into the cylinder if there is residual fuel pressure in the system. That might explain the fact that it will fire after you stop cranking, but won't continue to run.

One has to accept that the ECU is working correctly as it ran the engine prior to making any changes. That saves a whole other level of diagnostics...

It's kinda strange how troubleshooting a completely different EFI system (Megasquirt in this case) can bring to mind so many appropriate questions. The one thing that won't be an issue here that is regularly with the MS installs is people hook them up to a power source that switches off while the starter is cranking. They'll fire occasionally but will never run...similar symptoms but definitely not the case here.

Keep poking at it. Let us know what you find...

Dale