Is the ECM a '90 or the original 86.5? Plus, I've haven't seen a 'pin-out' diagram, but just the standard wiring diagram from the TSRM. This page,
Mk3 Supra TSRM (Toyota Supra Repair Manual) Links/Downloads , has a wiring diagram for the '86-'88, and the complete '90 TSRM. Maybe you can compare the two, and get the wiring harness to connect properly.