Help with ltft at 25.0

[not2oldchevy]

I have a 53 with a 5.3/4l60. Anything over idle I get ltft of 25.0. Engine transmission computer fuel pump all from 2003 avalanche that I drove with no codes. I have 700 miles on the conversion and get 0171&o174 codes every time I drive it. No vacuum or exhaust leaks. New fuel pump new tank new filter new 6an fuel line new fuel pressure regulator with no change. Fuel pressure is 50lbs with old and new parts. All fp regulators I have found foe this 2003 avalanche advertise 50lbs. I tried one for a 2002 suburban that was 58lbs but it would not fit. I also have a 1999 Z71 5.3 and a 2004 Z71 both hold 50lbs fp with no codes. I have no idea what to do next. Go POSTAL ????