hi,

No. I believe that yellow/red powers the overdrive indicator light on automatics. The red/ white is the one that you need to avoid putting in the wrong spot. If you don't have a tach, leave it alone.

I think a 90 should have a yellow wire from the cruise controller that would have gone to the double spade, and given you a vehicle speed, but I believe that was changed in 91 so that the double spade no longer provided that signal.

I was doing much as you are doing when I tried using an 87 cluster in my 91. I got a no VSS code. I was told the VSS was supplied through #6 pin on the big connector, I forget the wire color, might have been red, and it should work if the yellow was tapped into that. I never tried it because I was able to get the 91 cluster repaired.

There may be other things different with a 93, so get a second opinion before going too far. There are others here who know this stuff better than I do.

Peter