With the clear plug? Isnt the pink wire the jumper harness to connect 2 options to one slot?
Oh, I see what you're saying with existing plug. I'm not home where my info is, but is your car one that didn't originally have the rally gauge and tachometer gauge set? As Hoggie said, mine and most others have pink and black wires for tachometer and power windows, the jumper cable if both are used is also pink. It would also work if you needed both plugs but I think it's something else again.
I've seen that plug on my spare harnesses for cuts, can't recall what without looking.