Hi i've got an 03 wrx. while i'm idling, the engine will occasionally start to rumble and shake and the revs will drop way down and bounce up and down until i stab at the gas. this happens after the engine's warmed up and i've been driving for a while. any ideas? i'm going into the dealer for a recall sometime next month and i'd like to get some ideas on what's going on.

thanks fellas,

aftermarket bov?

what mods?

Do you have the A/C on? ;)

Nope, nothing.

bonestock wrx, and no AC.
when my AC kicks in, the revs actually rise, not drop.