I have used these tires (Kuhmo's) on my Porsche and know of many who attest to their perfomance. Perform just as well if not better than P-zeros. The only reason Pirellis ended up on Ferraris is due to marketing and what kind of deal they got. My car is already out of warranty and of course the Ferrari service managers are going to say that, just like they told my friend he had to use the Shell Helix or it will void his warranty. Do you think Ferrari would use Shell Helix if they didn't pour millions into their F1 racing? Now we all know that our engines wont blow up if we use Mobil 1 instead of Shell Helix. :lol: If that were the case every Porsche, MB, BMW, Viper, Corvette's engine would be history since they come with the stuff from the factory. Again, another example of Mobil 1 marketing with these companies. Which brings up another question, what about the guys who use 19 inch wheels, does the dealership reprogram their computers to adjust for the different wheel height? Don't mean to flame but I hate it when companies force you to use certain products based purely on the fact that the two are business partners. Sounds like extortion to me. :evil: