What is the engine size of a 1991 camaro rs it 350 or 305?

The 1991 Camaro RS could have either a 305 cubic inch (5.0L) V8 or a 350 cubic inch (5.7L) V8 engine. There was no single engine size for all RS models that year. To know for sure, you'd need to check the vehicle's documentation (like the title or owner's manual) or look at the engine itself.