2001 Headache!
 

I have NO clue where to post this as I am at my wit's end trying to figure out what might be wrong. 2001 4x4 with about 113k on it. Rebuilt transmission installed about a year ago (just about 17,000 miles on it now).

My problem is this...the truck simply doesn't like to run for long periods of time (this poses quite the problem since I often drive 100-400 miles a trip). It is perfectly fine when traveling distances of under 100 miles.

Last week, I drove 150 miles without a single problem...then I went to merge on to the highway, and it started to act possessed! When I put my foot down on the gas pedal, the RPMs would drop. They would bounce back when I took my foot off the gas pedal, but it's really hard to gain speed when you aren't pressing the gas... The truck shut itself off once...and twice I put it in neutral, shut it off and restarted it (seems to run fine for about 15-20 minutes after turning it off). It backfired once, and the Service Engine light flashed on and off, but now the light is not on.

I have already replaced the TPS, vacuum lines, spark plugs, battery, alternator (three times), air filter, and fuel filter. I also cleaned the MAF sensor.

Has anyone had a similar experience? I just don't know where to look now, especially since there is no light on...

Need to read the codes stored in the computer from when the light came on.