Surging, Bucking with new Kompressor C230

Help! We bought a new 2003 Kompressor C230 for my daughter in November of 02. One morning after we had had it for 3 weeks, she started it and the car began surging and bucking and making a huge noise. Also the exhaust seemed excessive. In shop, they could not get it to repeat this behavior and a computer check revealed no problems. We took car back but a week or two later the same problem occurred once again in the morning. This time they replaced a sensor at the shop. Once again within a couple of days the problem occurred again. The shop still could not get the car to repeat the problem for them. They did replace a number of things such as a fuel injector and some other sensors. On the
morning they were returning the car to us, they started the car and experienced the bucking and surging. A factory rep was called in and after another week, they decided it must be bad fuel so they cleaned out all fuel. They assured us this was the problem. One day after getting it back we had the same problem again. This past Friday they gave us a new Kompressor. Guess what today Sunday, my daughter starts the new car and it does the same thing. Please anyone, help!!!!!!