Because it is not driven regularly or street driven. The Boost is never on for any period of time. The problem here being it only sees that boost once in a great while. So it makes it seem that everything is hunky dori and then boom. It will break. But you go stock and I wish you good luck. But remember when you waste your motor trying to be cheap. How cool the race car with stock sleeves was runing 11.9's with that setup