Hi I need help my van runs great untill I slow down or stop,it starts to shake,now its to the point that I stop or slow down and it shuts off...ok about a year ago I did a major tune up-timing belts as well as the other belts,water pump,all the hoses spark pluggs ect. Even the disributor itself,changed all the o2 sensors even the knock sensor including the head gasket,fixed a couple of leaks in the intake as well,changed the gas cap,every where I take it they fix a little minor problem,,but not this one,what else can it be????? Gas pump maybe is week or some other sensors not working????please help me out.thanx