I have an 89 Audi 90, At car toys they gave me a Harness that fits VW'S and Audi's its made fromMetra its number is 1784. On this harness is a place for three of the four plugs to plug into. There is room for more pins, am I suppose to take the pins from the extra plug and put them in the other plugs? Also the color of wires dont match with the Ausi harness. Anyone know how to do this? or know where I can find out about the wiring diagram for the 89 90?

yes you do have to put the wires into the harness connector. also don't forget about running the blue turn-on wire to the amplifier wire. if you need exact colors. post it, i'll check mine.