Tac Module

What is it and where is it located? i've been doing some research into my problems, and saw one post on some other site that mentions a problem with the tac module and the pcm that will cause "Reduced Engine Power Mode" which will lead to

Acceleration limiting--The PCM will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
Limited throttle mode--The PCM will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
Throttle default mode--The PCM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
Forced idle mode--The PCM will perform the following actions:
Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned off.
Ignore the accelerator pedal input.
Engine shutdown mode--The PCM will disable fuel and de-energize the throttle actuator.

the last one sounds a lot like the problem im having

wow... no answer on this one?