Sounds like the TCC. But keep in mind that the VSS can also act up and cause it to engage and disengage. I have had this experience. I got lucky, all it was was dirt had got into the plug. Cleaned it and it was fine.
look straight up on the drivers side of the dogbone mount, youll see your trannys fluid lines, and an electrical connector with about 5 or 6 wires (not sure how many) coming from it, pull that connector, thats the harness that connects to the tcc, its also the only harness that connects to the tranny...
My TCC solenoid was acting up last year so I replaced it (its easy to do and you DON'T have to even jack up the engine to get the cover off if you work at it for a while). The solenoid fixed the stall problem but I'll get that jerk if I let off the throttle at higher speeds... I think it might actually be EGR valve closing a bit late when you let off the gas. Even with a new EGR valve it won't solve the problem, I think thats just the way it goes.
I have a brand new egr, but im going to unplug the tcc tomorrow and drive for a couple of days to see if thats the problem, also I can see a plug while standing on the drivers side of my car. Its right on top of the tranny, it this the tcc plug?