Code 54 95 Silverado 5.0

I need HELP as this is driving me crazy.1995 Silverado 5.0 4X4 212,000 miles.Truck is OCCASIONALLY stalling ,lack of power,hard start and a couple
of times a SES light came on but goes away after restart.Took it to my friends shop after work and he scanned it for me over a couple of cold ones after shop was closed,got a code 54,fuel pump relay.replaced it, no joy.Checked fuses,no joy.Cleared code and it did NOT return while we were working on it.Got on the internet printed wiring diagram to see what else is on same circuit.Oil pressure switch is on the same circuit but is not leaking so we ruled that out for now.Can't see anything else that it could be so he thinks it might be the computer.To test the computer the book said pull the wire off from the throttle position sensor and you should get a code 22,which we did although he still thinks it might be the computer.Taking it back next week for more head scratching but I thought I'd give you guys a wack at it.Problem is INTERMITANT which makes it a real pain to diagnos.Any ideas??? Also his Snap-On scanner wouldn't communicate with computer on truck but his NEW 5,000 dollar GM scanner did if that makes any difference which is weird cause the Snap-On always used to work on the truck.
Thanks Earl
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