the 65mm pulley, combined with a good cai, and a tune will net you a noticeable performance improvement. there have been problems with aluminum pulleys, so be sure to do your homework. there is a great improvement. 32Krazy can help you there, as he has built two them before moving on to a Porsche. Latemodel21 might chime in as well. He is running a set up on his 32.