strange problem, here is mine, when i first got my stang, my friend put a stock motor in for the time being, and the amp gauge would just drop alot and the car would do the same as yours. thought is was the alt. so i upgraded to a g3 and thought that would solve it but it dident. i then started messing around, shaking wires and stuff, nothing, then i finally double grounded the battery to the headlight ground and the problem stoped. since i had the new motor put in, i dont have to double ground it anymore and the problem has went away, so im thinking that when the stock one was put in, either something was messed up with the install or maybe with the connections with that motor. Is your car a stick, im thinking that is why it fires back up when stalled. when mine cut out and then fired back up i would smell fuel. do you smell fuel. ok, good luck