2000 gmc savanna 3500 5.7
Backfires and almost stalls when in reverse or drive with little or no throttle input.
New fuel pump
New cap and rotor
Not throwing a code anymore
Did throw a p0174 a few days ago but not for days
Have a live data scanner showing LT FLTRM2 at or near 25
Checked the one vacuum line I could find and vacuum was fine.
Fuel pressure about 62 burst holds at about 55 no drop when I turn the key off.
Cleaned MAF AND THROTTLE BODY.
Ran without MAF same problem
Also took it to a shop who said they tested it and couldn't figure it out. They also gave it back with the MAF installed backwards, we did it by accident but they never checked it. When I got it back I noticed it when I pulled the air box off.
Not sure what to do next.