It is the TFI wiring shield. It keeps the TFI signals from scrambling the other computer inputs. If it isn't grounded to pin 20 and body ground, the computer inputs from the sensors can be unstable.
jackpot i think we just found my problem. gonna work on that tonight when i finish going point to point on my harness. by the way thats a big pain. i pulled the harness last night and took off all the wrapping and have been tracing every wire checking continuity