I installed two 2" flowrites in my on the dash the same time I gutted the airbox and added the air horn kit. It made a difference in the sled. Actually it was leaned out so much that it wouldn't run unless I played with the choke and I had a shop rejet it for me since I'm not familiar with jetting. It seems to have more torque and pull but I think it has even more potential since my jetting needs to be tuned. Its a little rich but I did notice a difference on my 600 and when I'm wearing my MX helmet I can hear the engine rumble through the air box when its downshifting into corners. I did this "mod", if want to consider it a mod, after I put on hundreds of miles on the clutch kit and gearing so I was able to distinguish if there was in fact a difference by installing just the air horn and flowrites. I recommend doing the flowrites along with it to get the full affect and I don't think you'll regret it.
Scott
EPI PRO clutch kit, dropped one tooth on top gear,VForce 3 reeds, SLP Airhorn Kit, gutted air box, SLP 2" Flowrites, MBRP Trail can, 144 1" studs, Trail Blazer 6" carbides, Polaris security system, Sportech 3" articulating bar riser, Sportech flat black handgaurds, yellow skid plate, silverstar headlights, shock socks, custom aluminum windshield, flat black headlight cover, custom exhaust cover, and there are blue lights under the hood.