When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Mugen or Toda - proven gains. Toda works even better if you have a test pipe, Mugen is all midrange. Spoon has a huge dip at 7000 rpm - can't get rid of it even with tuning.