fuel pump pressure problem

HI,
I started a new thread to get a new subject line.
97 k1500 5.7 engine.
I replaced the fuel pressure regulator and no help with the problem.
Using the shop manual, I get to a dead end in the diagnostic flow chart.(It says look for a problem between the pinch and the engine.)
When the pump is powered, the pressure is 62. running it is 50-55. But it stalls when I shift into gear. The pressure drops some.
The pressure drops rather fast when the power is cut to the pump, down to around 15-20 lbs. So I'm trying to find why it drops.
Diags have me pinch the supply line first, the pressure still drops. Then pinch the return line, it still drops. When the return line is pinched, it will go up to 80 lbs.
So it looks like something at the distribution block to the injectors must be leaking.
I don't think an injector is leaking yet because I have no flooded starting
And under the upper manifold plenum, there is no gas puddles.
But I can't rule out the injectors for sure yet.
I'm going to check the library for a Mitchell book to see if it will help.
Or does anybody have the shop manual for a 97 C/K truck so we could email off list a few questions?
My book is a 96 and possibly there could be something missing.
Thanks,.
Bob B

OK I made a mistake when going down the diagnostic chart.
Turns out it now blames the 6 month old fuel pump.
So I added my own test: i pulled the fuel lines from the injector block and put a piece of hose on the supply line from the tank and clamped it off. The symptoms are the same, good pressure with power on the pump
and when I cut off the power, the pressure drops fairly fast.
So with just the fuel line and the pressure gauge involved. it has to be the pump .
Bob B