you are are a pure genius and very helpful man.
this car has had the AT swapped for an MT.
when that happened the idle was funky because we were running with the AT ECU at the time.
so my mechanic did something to the idle.
i've since did the MT ECU in the car and never touched the idle but now i know that is what is causing the problem and how.

and also that my understanding of MT is a bit messed up. I always thought it was safer and better to throw the car in N to slow down to stop. but now i think that is not even the correct way to do slow down to stop.