There are some years that don't have them, I may be wrong about the 90 but someone will chime in but I believe the 90 manuals had one and the 90 auto's didn't..
Look behind the supercharger inlet to see if you have EGR. If you do just swap it to the late model plenum, or if you dont they make EGR block off plates or just make one out of small piece of steel or aluminum. My 90 auto does not have EGR.