This might sound too simple and maybe it is but, have you verified all the injectors are securely in their seals with the hold down clips snapped in place? I wipe down my engine every time I wash the car. I polish several areas with armorall to keep it looking good. In the process hoses get pushed around a bit and I have a couple of injector clips that are a bit weak. When I notice the engine idling a bit rough I push the injectors down and invariably feel one of the weaker clipped ones go back into place. The idle smooths right out. The other area that occasionaly gets disrupted while I'm dusting things off is the electrical plug at the vacuum advance solenoid. With that unplugged the idle is noticbly rougher and I'd think either of these things could effect the emission testing. Bruce Benson