I have seen internal ECU issues cause this. The TPS driver is shorted.
To verify, unpin the TPS output wire at the ECM and leave all other wires connected normally. Then check the TPS output voltage with a multimeter key on, engine off during TPS sweep.
When you replace your ECM, be sure to remove ALL the foam padding from inside the plastic case if it is still in there. It should have been removed during a factory recall.