my 93 civic hatch with a b18b turbo'd engine has what seems to be a misfire. If i start the car when the engine is cold, it idles around 3k rpm and has no problems, and will run smooth even when it warms up, but once i turn the car off and then on again while the engine is still warm there is a misfire, the car will idle at below 500 rpm, when usually its at 1k rpm (when the engine is warm), and it will begin to shake... Someone had told me that the exhaust was smoking a lot when i left a parking lot when this low idling shaking misfire was occurring... Also, when this is all happening, my air to fuel ratio gauge doesn't work. My car has a Hondata s300 computer with a tune that keeps the boost at waste gate pressure, 4psi, if that makes a difference... i tried changing the spark plugs today, no avail...what is wrong?