Originally Posted by m4a1mustang

Only on the supercharged cars. So on the 550 hp GT500 you could spend about $600 or so on a pulley and a tune and make 650+ hp with the factory blower.

I think the '03-'04 Cobras were able to run from about the stock 390whp to 500-550ish on the stock blower with just a pulley swap.