My son spoke to me earlier today regarding problems with his 2.0 oil burner turbo bmw. As he was driving, he heard a loud pop, and the car lost most of its power. He says it will not exceed 40mph and is totally gutless.It is also throwing out clouds of black smoke. The obvious thought was that the turbo had let go, but surely the car should run at higher speeds with lack of acceleration, unless the ECU has the ability to limit the speed until the fault is cured. Any ideas?.