Porsche's 4-door Panamera will be finally unveiled at the Shanghai Motor Show on April 20 - not that we haven't already had plenty of chances to take a good look at it through the company's prolific PR department. Designed to be at once more luxurious than an S-Class Benz and sportier than a Beemer M5, the Panamera is the first 4-door Porsche with an uncompromising performance focus. It looks like a belter too, considering rumors that the 500-horsepower, US$132,600 turbo model actually had to be reined back in performance terms just so it wouldn't trouser the 911, which is supposed to be Porsche's performance flagship. As a brand new, extreme high end model, you'd be expecting the Panamera to pack a few technological punches - and you'd be right. Here's a few of the key innovations.