Depends on what engine it has...
215
the last production year for the iroc z was 1990, there is no such thing as a 1991 iroc z
93-97 z28 camaro's have 275 stock horsepower at the crank, not RWH.
The 1987 Iroc-Z with the engine code L98 (350 with Tuned Port Injection) was rated at 225hp.
245 horsepower
310 horsepower 325 horsepower
200 wrhp stock
285
200-220hp
310
NONE!
230 hp, or 240 hp with the dual-cat option