I’ve tried about everything in this truck, it’s got a new head gasket on one side and the other is fine, it’s got new intake manifold gaskets too, it’s got new MAP and Crank position sensors as well as a new idle air control valve and a new fuel pump/sending unit. It also has new spark plugs

It starts right over and runs fine initially but the longer it runs, the rougher it gets until it eventually stalls, if I put it in reverse it runs really rough and drops oil pressure and in drive it does something similar but not as bad. When it’s in drive and you go to hit the gas, it just has no go to it and crawls very slowly until it eventually picks up and then drives what you would call fine but that takes about 10 - 15 seconds and makes pulling out of a lot or my driveway a nightmare because it just barely crawls.

 

Aftermarket sensors don't always play nice with these trucks. Did you replace the parts trying to solve this issue?

Will the engine run ok for a couple minutes at cold start, and then start acting up?

 

I replaced them trying to solve my problem yes, the engine runs completely fine after cold start and idles good for the most part but can sometimes trip and then catch itself. The issue is when it’s in gear. If it’s not in park or neutral it just gets really rough and is extremely sluggish when it comes to the gas pedal.

 

Any codes? May want to check fuel pressure.

 

No codes and 40 psi of fuel at the rail.

 

Pressure is correct. Try unplugging the front O2 sensor, drive it like that for a bit. See if anything is any better.

 

So I unplugged the sensor and it hardly runs without it and just pressing the break makes the engine stall

 

Ok, that shouldn't happen.... Wonder if you have some leaky injectors.....

 

So the motor is fine for sure. The plugs are dry and the head gaskets are good and I tore it all down and cleaned it all up last week and put in new gaskets. When you start the truck and leave it in park you can rev it up like a race car flawlessly without any hesitation or issue. The problem comes when you put it in gear so I don’t think it’s the injectors

 

Did you happen to check it with an extended high rpm? Did it drop any? What about a stuck egr valve? Any vac leaks(pvc)? If you can a scanner that reads live data you might see what's going on. Wonder what the engine temp sensor is showing.