I have a 2005 auto/steptronic with 70,000 miles in general good condition but lately the engine wants to stall if i come to an abrupt stop,especially when it's cold out, below zero,winter time in general. The rpm will fall to a point that the car shakes violently and then stops shaking and rpm goes back to normal. At idle the car is fine ,nothing abnormal,no idiot lights in the dash and I haven't check if their was a code because I have no warning light. It seems to be related with the brake system,some fellow member sugested a defective vacuum hose or some parts related to the brake system,any ideas supporting this. Problem seem to dissappear when the engine warms up but it takes a while,help please,thanks

Michel