 The engine ratings carried over from '88 with the addition of IROC-Z Coupes had a new dual catalytic converter exhaust option N10 that was standard with the G92 option only available on the 305 TPI motor with a manual transmission and the 350 TPI only available with the TH700-R4 automatic.1989 was also the last year any third-gen with the B2L RPO 350 TPI L98 engine could be ordered in combination with the CC1 RPO removable T-Top roof panels.Power ratings also varied in the 305 from 170 hp (standard RPO L03) to 230 hp (RPO LB9 with manual transmission and RPO N10 dual catalytic converter exhaust) and a boost to 240 hp for the 350 with RPO N10 respectively.