what are the symptoms you are experiencing? I would think by 89 you would have the later/updated style of injector.
There are two ways to adjust the mixture, one is the tower in front of the fuel distributor which effects mixture up to 2500 rpm. The other is the EHA, the black box strapped to the side of the FD.
You can read up here on adjusting the CO:
http://landiss.com/mixture.htm
Jonathan