[Joe Wicked]

If keying the mic is causing a misfire, it sounds like either something is not wired in correctly, or it is pulling too much of a load on the system. If it is a momentary load, and then the car runs fine, while the mic is keyed and you are talking, then I would suggest a large capacitor be put inline. Similar to what is run in high wattage audio amps. If it is a continuous misfire, then either the device is wired wrong and creating a short, or the electrical system is operating at it's max and as soon as you use more, there is not enough juice to keep the car running. I would expect battery charging issues with the latter.