Mark - the first thing I would check is the TCC wiring. I'm sure you know this, but on the Gen III motors, the TCC wire should be receive 12v when the brakes are off and then a ground signal when the brakes are pushed. Do you have HPTuners? If so, you can actually set the scanner up to data log when the torque converter is locked or unlocked.
As far as the second problem, that could be an issue with the Force Motor. Actually the more I think about it, they both could be caused by a problem with this. Here's a few threads I found on HPTuners forum:
http://www.hptuners.com/forum/showth...-Highway-Speed
http://www.hptuners.com/forum/showth...ht=force+motor
http://www.hptuners.com/forum/search...earchid=814209
Let me know if any of this helps.