I have a 91 sho and I experience random idle problems from it. Sometimes my car idles fine, but most of the time when I am in neutral the engine revs up and down, and occasionally it will stall, but usually it just bounces somewhere between about 500 and 1500 rpms. I've changed the spark plugs and wires, the fuel pump and filter, the act, tps, and maf sensor, and the iab valve. None of this has affected my problem. Does anyone have any suggestions? I was wondering if it may be bad fuel injectors or regulators? I recently bought stuff to put in the fuel tank to clean the injectors.