My 1997 chevy tahoe will not start without starting fluid. I hear the fuel pump running and have changed the fuel pressure regulator already and the fuel filter. The pump is only a year old. Have checked for fuel pressure upon starting and it is really low and sometimes there is none, but my truck runs fine once it's started and if I drive it for a few miles and turn it off it will start on it's own (without starting fluid)as long as it's only turned off for 5 to 10 minutes. Can you help?? any suggestions what might be wrong?

IVE HAD PLENTY OF THESE GO OUT EVEN A MONTH LATER. AS FAR AS THE STARTING FLUID JUST TRY AND CYCLE KEY BUT KEEP IT FROM TURNING STATER OVER. TURN ON AND OFF ABOUT 3 TO 5 TIMES IT SHOULD BUILD ENOUGH PRESSURE TO START. TO START MINIMUN PRESS IS 55PSI.

97 chevy Tahoe 5.7.
New EGR value
New fuel relay fuse
New coil
New cap and wires
New fuel lines
New gas filter
New housing for the fuel pump. Everything wiring grounds filter.
New fuel pump 10 months old.
New tank and air filter
All brand new of last week.
Dam truck will start but barly on the 1st try.
when running it sounds wining cools down fine but when you punch the gas pedal truck dies on 2000.00 Rpms unless you get it over by featuring it will die.
I ran a fuel presure test I come up with 50 pounds that weak but enough to run it.
Should be 60 to 66.
i ran a code scan i come up with EGR which I replace or it's leaking air.
Next was O2 senor which I do not no if it's down or up hill one.
Last O 2 senor on the castaic.
No check engine light.
How do you no
it's not the Map senor
the fuel regaltor
Or Should I replace the pump again.