P38 seems to wanna die at low RPMs...
 

Hopefully, this is an easy one... tried the search function to no avail... Randomly, my 99 P38 4.0 when coming from a complete stop, and especially off a cold start, will try and die somewhere between 800-1250rpm, anything past that and it will run/drive just fine. It will idle at 750 just fine, but when I put it in gear and hit the gas itll kind of shudder till it gets to about 1300rpm, if I let go of the gas during said time itll stumble and drop dead unless I get back on the gas and bring the tach up, and then will run as if nothing happened.... fuel delivery maybe? This is really the only issue I have with the truck... it doesnt appear to leak anything... or anything like that... no overheating... Put it up to my computer and found it had been misfiring, (previous owner ran 87 thru it for a while), an MAS error. and an unknown error that I think was p1884 or something... any help would be great, thanks!

MAS error? Do you mean MAF? This sounds like a MAF problem anyways. P1884 is some what of a mystery. Engine friction invalid, is what I found, and that on the discovery it can mean something with the transmission. Don't know if its related or not. Do you get a check engine light or faults displaying in the instrument cluster? You need to get it on a scanner that can read live data from the car to determine what the problem is more accurately

I would start with cleaning the MAF sensor.

Cleaned my MAF today. Not much difference... Still getting P0102 - Mass or volume air flow circuit low input -and- P1884 - Unknown Diagnostic trouble code.

Thanks for the help, you guys narrowed it down for me. Changed the MAF today, cleared the codes, and the truck runs great again! Now just gotta wait for EASunlock delivery, so I can bring all four corners to the same height.