I have a wire that i'm not sure what they are for and was hoping you guys could help me out:

The purple wire with the grey plug is under my dash behind back by the fire wall and looks to come out of a big bundle of wire. any ideas on what this is for?

 

On my car i think i have a big wire like that by the front of the DS door and it connects to a purple big wire and goes through the ducking along the DS door.
If it isnt that it might be for where the wiring would be for the Clutch safety switch on a manual car. I know that has a big purple wire. I cant remember if it has a white tracer though.

 

I've been pulling the dash and wireing out of a 90 firebird v6.I traced a big purple wire from that area and conector type all the way back.I came out to be the rear window defoger.If you got a grid or had one thats probly it.It changes to black just as it comes out of the harness about 6 to 10 inches from the end.Why do they do that?

 

To confuse everybody so you have to pay the dealrs to fix things : ).... Thanks guys doesn't sound like anything I need to worry about as my car is an auto and dosen't have a rear defogger so ill just tuck it up out of the way.