Someone (can't remember where I saw it) dynoed a stock Rocket, then removed the seat so the stock filter wasn't sucking through the seat snorkel and it gained a few hp immediately. I think a few people removed the snorkels from the bottom of the seat and noticed it flowed better.
Paul- All engines are going to suck a fixed amount of air, but the easier it can pull the air the faster it revs and the faster it goes. The temp difference won't matter much at all once you are rolling. There is quite a bit of air that gets under the tank. Plus like the others once I got the under seat storage I can't give it up, too handy. If I recall correctly I think our own Toystoretom was the inventor of the under tank mod.
Hey Travelguy forgot to thank you for the vid.