There is an easier way to do this.
http://www.supras.com/04/resources/index.php?id=44&q=tems
TEMS Firm Override, Cockpit controlled FIRM mode
Updated: Dec 5, 2003
Generation: MKIII _ 1986.5-1992
Category: Body Electrical System
Article
Authored by: Jeff Montigny, SupraSport.com
Tools Required: Wire strippers/cutters, Elec. tape, Solderless connectors, Off/On Switch (mountable)
Skills Required: Wire stripping/splicing
Access Diagnostic Block and Wires
It's in the engine bay, next to the fuse block and battery.
Locate Ts=Violet, E1=Brown wires.
Plug wires into top or splice leads into bottom of block. (Tap into, do not remove stock wiring.)
Feed your wires into the cabin (I cut hole under clutch pedal).
Connect Switch
Use a easy access off/on pushbutton.
Place the Ts and E1 leads onto the two terminals.
Operation
Push button on:
If TEMS -NORMAL- is on, will have steering wheel feedback by the blinking TEMS indicators.
If TEMS -SPORT- is on, will have FIRM locked in!
Push button off:
TEMS has normal control, with -NORMAL- and -SPORT- control.
Notes & Additions:
11/10/01 - Paul L. - on my 87 Turbo, there is nothing labeled as Ts in the diagnostic connector, it is labeled TEM