This weekend, in the Makuhari Messe of Tokyo’s Nippon Convention Centre, tens of thousands of car nuts will visit a motor show totally unlike the one about to take place thousands of miles away in Detroit. Few in the automotive industry would deny that Tokyo’s Auto Salon lies firmly in the shadow of the North American International Auto Show (NAIAS for short), but it’s vibrant and interesting nonetheless.This is Japan's premier custom and tuner show. Once upon a time, the Auto Salon was this kind of wild, outlaw event. Today, like America's SEMA show, it's gone increasingly corporate. All the big Japanese car-makers have official stands and a host of production models get the aftermarket treatment (body kit, wheels, tyres, suspension kit, exhaust etc) with factory blessing.And the Auto Salon was heaving again this year, on first press day today, and car of the show was unquestionably Nissan's GT-R. They seemed to be everywhere even though the GT-R's still so new and supposedly in short supply.Nissan, of course, has gone out of its way to spoil the tuners' creativity. After years of rogue 600-800bhp Skyline GT-Rs roaming Japanese roads, the new GT-R has a limiter to keep power at 473bhp and Japanese mandatory top speed of 112 mph for the road very much in check. Why? To keep the Japanese transport mandarins happy.The smartest tuning brains are now trying hard to crack that, of course. So for now, most were limiting themselves to wheel and tyre conversions. But one outfit called Blitz is already talking about a power jump to 519lb ft. Quite how they will manage that remains to be seen, as the GT-R management system is very hard to hack into. This time next year, though, with Nissan's own lightweight, high-power Spec V version of the GT-R on sale, maybe things will become a lot easier.At the Auto Salon, Nissan also unveiled the wicked-looking silhouette race version of the NISMO GT-R, destined for this season's Super GT series in Japan.