new cars will draw 0.2 of an amp ... in shut down mode, it changes from car to car, once u got it narrowed down to one circuit it looks like your tracing wires.
cars will always draw some current, the more security and convenience features the more it will draw even when its off. if I remember right I have seen figures of 0.5a being normal draw for a car that is shut down. why do you think you have a parasitic draw ?