I have been driving a 997 PDK 3.6 2009 demo car, getting a 997 PDK 3.8 tomorrow for the next five days and have a concern about a weird sound that is coming from the engine / transmission of the car. When I am coming to a stop or going around a corner from standstill - ie pulling away slowly at a corner or a crossing I get this strange guttaral sound - hard to describe - like a knocking sound almost. I have experienced it in another 997 PDK too in addition to my friends AMV8.  Any idea's? Appreciate your input....