89 Dynasty 3.0L Drivability problem

This is a long story, but I have to start at the begining.I picked up an 89 Dynasty for my girlfriends kid to get back and forth to work. At the time I picked it up, I knew the car had a problem, but the way it was acting at the time, didint seem to be to big. Boy was I wrong, So here we go, The car had sat for approx 3-4 yrs due to a loud lower end noise, the guy I got it from installed a known good 3.0L (1992) thinking all would be well, he started getting all kinds of codes and finally gave up
I had the car towed to my house and started to work on it. The engine would idle so good that you could set a glass of water on top of the plenum and it wouldnt even ripple. It will back out of the driveway and accelerate fine a little ways down the street, but after stopping at the stop sign, when you try to take off it acts like a older carburated vehicle with a worn out accelerator pump. The only code I got was a code 24, not having a book on this vehicle and knowing a 24 is TPS I made the mistake of purchasing a new TPS from my friendly AutoZone man. While there, he printed out the procedure for trobleshooting the TPS circuit. After walking through this procedure and everything checking out fine, the ECM was pointed at, I installed a known good ECM with the same part number. Now I get no codes except of course 12 and 55, but the vehicle still demonstates the same problem. I have access to a DRB scan tool so I brought it home only to find I dont know where to hook it up, the plug on the scan tool does not match up to any port I can discover on this vehicle. ANY HELP would be VERY GREATLY APPRECIATED.............................