Hey guys...ok i have a 91 camaro rs, 3.1 V6.(yeah shes a little girl... im going Lt1 eventually). When i have it in neutral it runs rough, but will still rev up. When i have it in drive it runs very rough, and wont go any faster than about 30mph. I changed my plugs and wires.I also put a new distributor cap and rotor on. Last time it did this the shop said it was caused by the hypertech prom i put in the ecm. It had caused a plug and wire to foul. The prom was removed, and the problem seemed to be fixed. Now its back. Im thinking that it could be a clogged catalytic converter, but before i unhook it to check i wanted to make sure that i knocked out the simple steps. Is there anything else??

-BOOM Montana

try a fuel filter first...