ya it can be annoying. there are some extremely stupid reasons why certain cars cannot be smogged. the worst example are 1996-2002 VWs and Audis. whoever designed the wiring harness that goes to the diagnostic port, had a wire also go to the radio, the k wire. anyway, when the first company made a wiring harness for an aftermarket radio to be put in, they saw the nice juicy 12 volt line and tapped into it. everything was fine until those rides had to start being smogged, and smog machines were blowing out. turns out when they tapped the wire, it sent a bunch of voltage back through the connecter to the machines and was blowing them out. dont you just love some engineers.