Fueling & Injection - Loading up issue? maybe

My question is the fuel pump from an lt1 same as ls1. I have the ls swap and it runs fine in idle. But as soon as u give it any throttle it falls in its face, in park. Also does it in gear. Not sure what the flow rate or psi is. I have a 1994 z ls swap. I have the Corvette fuel filter so I have the return line.

Please any help

An original LT1 pump??
How is the system plumbed? [You mentioned Vette regulator.]
LT1 is run at 3 bar, LS at 4 bar.
Until you find out what the fuel pressure is, U R shooting in the dark....

It's an lt1 pump. I checked tha plugs and there black.

Isn't there a Inline fuel pump u can use with this lt1 pump and use a fuel pressure regulator?