what does it do if you take off your air box lid? thanks Joel

 

It allows more air into the motor to gain power, but most of the time you need to rejet to take advantage of it. It also makes more noise.

 

You will see bigger gains on some bikes as opposed to others..Take the 250R for example..It already had a great airbox design so the gains would be minimal, but on a bike like a banshee or blaster where the airbox design isn't that great you will see bigger improvments..

 

It will give if you add on a better air filter and re-jet you'll gain a couple horses. I'd add a prefilter on too.