Well,,, On my Grizz 660 I installed the Dyno Jet Kit and ran it for 1000miles-It made a descent difference (more response on low end) I rejetted a min of 7 times for adjustments to get it just right. My top end was knocked down consistenlty by 3-4 miles per hour. So.... I put on a dial-a-jet and immediately got back the 4 mph on the top end.

I ride anywhere from 5000 ft to 11,000. Seems my quad really likes 7000 to 9000 the best. The dial-a-jet works good for high altitude riding.

Only downside is you have to be willing to rejet several times to find the right mix.