I had an 89 Spirit 2.5 Turbo I that had a wastegate issue, and so was over-boosting. Instead of bucking, though, it simply felt like I'd let off the gas pedal, even if I kept it floored. Once the RPMs dropped to a certain point, it would pick back up again. I never had a CEL. I know this is 89 TI vs 87 TII, so there may be some differences, but thought I'd throw it out there. Wish I could remember more specifics, but it's been several years.