Definitely N rated. My favourites have been Continental; currently running Michelin Pilot Sports which are also very good (low noise, lots of grip). The N rated pilot sports actually have a different tread pattern to the 'normal' pilot sports
I've tried Bridgestone so2's, Contisports, Pirelli Assymetricos, and Michelin Pilot Sports, all N rated on my 993 C4 and my GT3 Mk.1. My opinion is that the Michelins are best for all round general use.