 When I purchased this car it was like driving a pocket rocket....loved it!  I took it to the dealer, for maintenance, and when they gave it back to me it didn't have any of the acceleration anymore.  I've been trying to work with Nissan and their dealers to get it back to my "original" experience.  Most dealer techs acknowledge that it doesn't perform the way a 3.5 SR should be performing; acceleration, handling, etc., but will only tell me that it's operating within specs.  The problem is, it seems that the dealers have (at most) only received one of these models so they're not familiar with the difference of having a 6 cylinder versus a 4 cylinder under the hood.  I don't know what to do, but would warn anyone thinking of purchasing the 3.5 SR....don't.  You may think you're buying that "pocket rocket", but after the dealer hooks it up to their diagnostics, you'll be driving the 2.5 version.