With the seventh generation 911 now launched, Porsche is hard at work preparing the next round of extreme performance variants like the Turbo and GT3. Our spy photographers captured a 911 Turbo and Turbo Cabriolet undergoing winter testing, along with a craftily disguised GT3 spotted at night. Both Turbo models at least have the benefit of standard all-wheel-drive, to cope with those snow-covered roads. On the other hand, the...