Engine surge and stall

Okay, so here goes nothing. As I said in the description, my truck listed above is an XLT extended cab. It has a 2.9 engine, it's two-wheel drive and is a six cylinder. The truck was a gift from my grandfather for completing my freshman year in college. I'm not exactly sure how long he had it before passing it on to me but even before it was given to me, it had problems. To begin with, my grandfather would have to let the engine "warm up" before driving it and as time went on, the problem worsened. When he would drive it, he had to keep his foot on both the brake and accelerator to keep it from shutting off. It would not hold idle. The car would shut off almost immediately. The first chance I got, I had a long time mechanic friend take a look at the car. We replaced the plugs and wires, as well as the fuel filter and for a time, that seemed to help the car hold idle but I noticed that when I would stop at a stop sign, or traffic light, the engine would begin to surge again and would die if let to sit for too long.
Now the problem has once again worsened. So much so that, there are points where the care will not start. And when it does, the second I take my foot off the accelerator, the car will - once again- shut off. I have had it begin to skip (that is to hitch) as if it is trying to shift gears (it's an automatic) and if I take my foot from the accelerator, or put it on the break, the car will die. This has happened quite a few times while I've been driving (thankfully, there has not been a wreck due to this). I have had several things done to the car and that list is as follows:

1. Ran the trouble codes multiple times- Each time it has come up as the Throttle Position Sensor.
2.I changed the spark plugs.
3. Changed the wires.
4. Replaced the distributor cap.
5. Replaced the distributor rotor.
6.I have had the throttle position sensor replaced twice, twice. As well as had it checked twice to ensure proper install and adjustment
7. I have had the oil changed.
8. I have run a bottle of fuel line cleaner through the engine.
9. Ran two cans of sea foam through the engine.
10. Cleaned the throttle plate.
11. I had the MAP sensor replaced.
12. Had the MAF sensor checked (was with the gentlemen and he said it was working).
13. I've had the timing corrected.
14. Changed the fuel filter.

My apologies for the long list, its just that, I've sank so much money into this car and I need it so I can travel back and forth from the college I attend (which I will be returning in a little over a month). I have been told it could be the computer, or the fuel pump and I'm just not sure anymore. Please, I need to make sure it's running well before I leave can someone tell me what the problem is so I can get it fixed and remove the stress of this situation?