I cant speak for Porsche but the Audi 'Tiptronic' greabox is a traditional auto box but with the ability to overide the box'es gear selection and select the gear yourself either by using the 'toggle' feature of the gearshift or the wheel paddles. The in 'tipronic' mode the box wont let you select a gear the engine cant handle at that moment and will automatically change up or down if the extreme for that particular gear is reached. The Multitronic box (the continously variable box) also has this feature in so far as you can toggle up and down the 7 'virtual' gear positions offered throughout the whole constantly variable range. The 's' tronic is just the new name for the DSG box. Are all three of these Audi boxes available in US? perhaps they have different names?.