We dropped the RS package at the end of 1997.There was a reason. The RS Package up 'til '97 on the 4th gen was only available on the V6...you may recall that it had a ground effects package. The Ground Effects package could not be put on an LT1 because the Camaro is a 'bottom breather' --meaning that the air to the radiator is guided by the air dam under the front of the car. The ground effects package would partially disrupt the airflow--and under severe conditions, you 'might' have the chance of overheating the engine. (believe me, it was very unlikely, but our validation procedures did show there was the possibility, thus, no V8 RS ground effects package.
IN 1998 when we redid the front of the Camaro and dropped the LS1 into it, the overheat condition was no longer an issue -- and we thus offered the "Sport Appearance Package" (RPO Y3F)
--The reason for the overheat no longer being an issue: you'll note that on the '98 - '02 ground effects package, the front fascia extension does not go the whole way across the front fascia....thus, the airflow is not disrupted.
The RS nameplate came back when SLP began to offer the RS package (RPO Y3B) by adding the Z28 exhaust, the dual stripes, and SS-style wheels.
Thus...there were no 1998-99 RS models from Chevrolet. If someone has one with the nameplate on it, it was added after the Camaro left Ste. Therese.