1990 was an odd year for Camaro production. The 1990 model year came to an end in December, 1989 because Chevrolet's contract to sponsor IROC ended at the end of 1989. Chevy then thought it necessary to re-introduce the Z28 and begin the '91 model year, with some new cosmetic changes for the Z28. The 1991 model year began in January, 1990, and the '91s were in the showroom by March, 1990.

The RS's base engine was enlarged from 2.8 to 3.1 litres for 1990. The engine only gained 5hp, going from 135 to 140hp. However, torque improved a more impressive 20 lbs/ft, from 160 to 180 lbs/ft of torque.

Standard, RS coupe: LH0 3.1 litre MPI V6, 140hp (12,743 produced)

Optional RS coupe, standard RS convertible: L03 170hp 305 TBI V8 (16,736 produced)

Optional, IROC: LB9 305 TPI V8, 210hp auto, 220hp manual* (3,092 produced)

Optional, IROC: B2L 350 TPI V8, 245hp (2,415 produced)

*With G92 package

Other changes for '90 included a revised instrument cluster with yellow graphics, drivers airbag, and speed density programming replacing mass-air on all engines. The IROC's 350 gained 5hp from this revision, going to 245hp. 62 1LE IROCs were built in '90.