I've noticed, when the car is in drive, it is fine... but if the car is in drive, and the fan is on (no a/c) it shakes, and even worse with a/c..
It sort of "searches" for the idle speed, it dips below 500 and then it goes close to 900 and then it settles at around 650, a bit less.. and is still kinda rough
i had the problem before i changed the leads though...