You want to use aftermarket underdrive pulleys? I have to agree with the other guys. I'm not too sure about rotaries. With a cylinder/piston motor using different underdrive pulleys will throw off engine harmonics and produce extra wear on main/rod bearings. Thus reducing overall engine life and reliability. I suggest you learning more about the car. Who would you rather trust? People on the internet who you have no clue about what their intentions may be? or Yourself after you get information and make yourself smarter in the process. Additionally if you really want to learn about your car. Visit these sites.

Mazda RX-8 - Wikipedia, the free encyclopedia

www.rx8club.com

Hopefully this helps you. I know the mazda forum in TR isnt really too active, so this rx8 specific forum might be useful to you. Don't mind the aholes here as there are aholes everywhere. Specially in Tampa. If you need any more help or advice let me know PM me or just write another comment. Im sure there will be some users here willing to help you as well. On another note

HOPE EVERYONE HAD A HAPPY TURKEY DAY!!!