Hi gang - my car is an 88 GTA. During this year they made a Digital Dash instead of the stock 'gauge' type dashes. And if you have one of these, you may be having the same difficulty as I did just FINDING wiring diagrams for this type of dash. Fortunately I found a copy that assisted me in wiring KITT's electronics to the car. Perhaps it may help you as well.
Here's a link to my Photobucket library page that stores the PDF diagram. Unfortunately I have to "trick" Photobucket and change the file extension to "JPG" for it to upload. So when you come here you'll see a blank picture. To get it, click OPTIONS (just above the blank picture) > DOWNLOAD. Once downloaded, change the file extension to PDF. That's it. Hope it helps!