i went through a beesh of a time trying to get my EDM cluster to work properly on my 88rex si. first i just pluged the EDM cluster in and it worked all funky, so i took the pins out with a needle and then matched up the wires to the EDM harnesses then it worked sum what properly. then i came up with a bright idea!!! get that flimsy circuit board off of my orignal cluster then switch it to the EDM cluster. after this i had to switch the wires in the harness back to where they orignally were (lucky for me i wrote the wire colors and the locations). now it works like stock!!!

 

Sounds like you did things the hard way.
All you have to do is swap the "guts" of the EDM cluster into the
USDM cluster (tach and speedo).
Everything bolts right in with no problems.