You also have to do a bit of rewiring for this to work in the 87-88 cars
(in teh 89-91's it is a basic plug and play).

You have to run 2 wires from the back of the alternator inside the cabin by
the ecu. Compare your old NA wiring harness and trace the wires that used
to be at the alternator back to the plug they ended at (one of the 2 large
orange ones inside the car). Now compare these pin positions with the
current harness. Cut whatever wires are presently there (theyre not doing
anything important) and splice in your 2 newly run wires. Be sure to cut
and insulate those old wires, so you're not backfeeding through some other
circuit. This keeps all your idiot lights from staying on all the
time (this is normally an indication of a failed alternator, and the car
thinks it has failed because the wiring was missing).

You also have to run 1 wire about 6 inches. On your old NA harness, find
the yellow/red temp sensor wire that went under the oil filter. Now find
it's pinout position on the orange plug that was inside the car. Compare
this to the turbo harness' plug. Now trace the same wire on the turbo
harness in the car. Cut that wire on the *engine side* of the turbo
harness, and jumper it over to the wire that is in the pin position the old
NA harness had the wire at. Be sure to cut this old wire and insulate it to
prevent backfeeding through that circuit. Now your dash temperature gauge
will work like stock