Porsche is a part of automotive history and legend for its two-door sportscars, but that hasn’t stopped it from veering slightly off its track. First, it built a sport-utility vehicle, the Cayenne. Then for 2010, it introduced the Porsche Panamera, the brand’s first four-door car. The Panamera lineup now includes Panamera 4, Panamera S and 4S, Panamera GTS models, plus the top-performance…