The EBP SENSOR, there is a tube that connects to the pass. side exhaust manifold. This tube looks like a brake line and goes to the front of the engine just behind but ontop of the pulleys. This tube will get plugged up with exhaust sot. From my readings some after market tunes use this for fuel mapping, and also it is used for trans shifting.
I looked at mine the other day since the truck always shifted funny. The tube was rusted in half and blocked by crap. Just ordered a new tube today from Oriley.
Some people say they loose boost when this gets plugged. Worth a shot.