You are not understanding the TPS sensor role in the system. The ECU changes fuel pulse based on the MAP,IAT, and engine speed. The MAP sensor reflects what is happening with the throttle position. ECU in turn changes timing based on similiar parameters and the engine revs up. TPS has few other functions, but the main one is for the ECU to produce a "accelerator pump" shot when the throttle position changes rapidly. Typically this is a time/distance ratio.
Before you go changing anything, I would get the codes read. If it is the TPS, it should show up. If there are no codes, I would not be surprised if it was the ECU. It almost sounds to me like it is running in "limp home" mode. Sounds silly, but this is usually a backup set of parameters so if something goes really wrong you can "limp home".