[40cpe]

First I would disconnect the feed TO the circuit breaker and check for draw. If it still has the drain, go back toward the source at every connection until there is no drain.

EDIT: I didn't read your last post correctly. When you disconnected the fuse panel, the drain went away. So your circuit is good to that point. You either didn't remove the faulty circuit from the panel or the panel is partially shorted to ground. Remove the fasteners that connect the panel to the car and make sure that the fuse panel isn't touching the car's metal anywhere and recheck. If it is still has the spark you didn't remove something from the panel when checking previously.

More thoughts: Maybe you have more than one appliance in the car that has a memory draw. Try removing all the fuses from that panel at one time and see if you still have the drain.