Check and verify no wiring mods were made. Also, how about the tugging on harnesses? Have you removed the stereo completely, tried it that way?
It is possible the stereo job and the throttle dying are just coincidence, but that is unlikely. You need to check every aspect of how the wiring was handled and affected. Do it yourself, or have a 3rd party do it. The installer (any installer) will have trouble spotting a mistake. Once a mistake is made, it is human nature to "see" things the way we know they are supposed to be, not the way they actually are.
PS: Question for others, where is the TAC module that has no com?