1994 gmc Sierra 5.7. Wont time right and backfires.

I have a 1994 GMC Sierra 1500 with a 5.7 350 TBI.
Truck was running rough at high rpms when i got it.
Changed sparkplugs and put ngk wires on it. Ran
better but had no power,  distributor was off so
retimed it by ear and ran perfect all kinds of power.
Then it started to roll over worse and worse
everyday and backfireing more again. Then almost
wouldnt stay running and would stall and wouldnt
idle like it was out of time. Pulled the distributor out,
changed the ignition control module, brand new
coil, new cap and rotor button and fuel filter, and
idle air, checked the egr and seems fine, and my
ngk wires were toast wouldnt stay on so bought
new wires again. Sometimes you can time it and will
idle perfect and if u slowly accelerate it will rev to
5000rpms no prob but if u do it quick it bogs out
and flutters. Can barely get it to stay running to time
the ignition now and backfires soon as u start it no
matter where i put the distributor.  Havent had the
truck even a year yet and replaced alot of parts and
still at a loss for what could be the issue.  Cant even
set it at 0 degrees with a timing light and the
iginition advanced wire unplugged.