The TV (throttle valve) cable must be adjusted correctly for the transmission to shift correctly. However, this will not cause the motor to lug and stutter. The Torque converter will just spin faster and the motor will act as if nothing was attached to it. The TV adjustment procedure is pretty easy, but it seems like it requires some finesse I think. Pull the TV cable out of the throttle body arm and push the adjuster in so that it's flush. Then put it back into the frame, attach the cable and pull the throttle open all the way by hand. This should adjust it to where it needs to be.