I would start by checking the adjustment of the control pressure bowden cable. That's what controls when the transmission shifts. I just checked the FSM, and it should be adjusted just like the diesels... where the cable rests should be where its freeplay stops. It sounds like your car has the cable screwed in too tight.
You want to adjust #43 until the end of the cable is sitting at the end of its freeplay when #13 is at rest. (IE, you can wiggle the end of the cable just a bit before you feel more resistance)
-Jason