I'm looking to purchase a '97 1.8t quattro. The car has 101k and the interior and exterior are almost perfect, but while test driving the car, my father and I noticed a bit of knocking in low RPMs in 2nd gear. Also, the presence of the turbo was faint, and there was no audible whine, even in higher RPMs. We asked the seller after if he was using premium fuel, and he said that he had been putting regular fuel in the car. So my questions are: is it worth taking the chance that no damage to the engine has been done and get the injector system cleaned or not? And if I buy the car and start running it with premium, will the engine knock disappear and the turbo come to life?