The position of the TPS is critical to the ECU which uses its 'zero'(idle) position to determine the mixture. From that reference point, as the throttle is opened the voltage output from the TPS changes, and the ECU uses this as one of the inputs for further determining the mixture.
On the early K series the TPS was just an on/off switch, but the later models the TPS varies over its whole range.
I would suspect either a badly adjusted TPS to start with, or it is damaged such that the voltage output is missing, or the wiring from the TPS to the ECU is damaged.
Mike