So I did a search and found some similar problems but this one seems to combine all of them:
My rpms are randomly starting to bounce- the car will drive normally for a while then all of a sudden when driving slow enough to notice it (ie rpms low enough), the revs will start bouncing from ~1000 to about 1600 all by themselves. Even if I take my foot entirely off the gas, the car will sustain its speed and the revs will bounce.
Under braking, it lurches as if I'm still tapping the gas pedal simultaneously.
Things to note:
-When I knock it into neutral (it's a 4AT), the revs will rise to about 2000 and stay steady while car is moving.
-Once I've come to a complete stop (whether it be in N, D, or M), the idle level returns to normal.
-It started happening when the car was warm (half an hour into driving), temperature outside ~72 so it's not a cold issue.
-At high revs, the rpms don't bounce at all. Once you've reached a low enough level they start to.
-I've tried disconnecting the negative battery terminal and reconnecting after a half hour or so... it still does it.
-Can't find any vacuum leaks.
It's a 6i, 4AT, about 25K miles on it.
Been doin it all day - won't be able to get into the dealership till Monday.