Originally Posted by MMC Racing

This is not true for emissions. Going up 1 or 2 sizes (well, down actually to a smaller pulley on the blower) with proper tuning (and CATs still on the car) will pass every sniffer test out there. Specifically to California and visual inspections - you would have to go to a smog testing center that actually knew the correct diameter of the stock pulley and remember to measure for it. Same with getting a hood popped by a cop. This is really a non-issue. Absolute worst case is you change pulleys and get reinspected.

As to additional wear on a vehicle, we can look to the 350z community and see how many people went to atleast the 3.12" pulley as an upgrade and how the engine has held up.