1990 No Up Hill Power?

[LynnJr]

I have a 90 350 tbi 5 speed 4x4 that doesn't have any error codes in it.When I go up a hill blue haired old ladies pass me up.It cuts out like its starving for fuel or fouling out atleast 2 plugs.Once I get over the hill it runs much better but still doesn't like anything with some throttle in it before it starts cutting out.
I replaced the entire fuel pump assembly and measured at the filter running it looks like 10 psi.
I replaced both injectors and the filter.
I removed the catalytic converter and am running a test pipe.
Most of the small parts on the exterior have been replaced atleast once.
I replaced the computer but not the circuit chip that goes on it.
I am starting to think it is electrical.
I am the original owner and the motor is a newer crate motor from GM with probably 20,000 miles on it.
Any help or ideas are appreciated.
Lynn