Need for Speed - Air Filter Dilemma

Well, I checked my rear sprocket and it is a 46 tooth. I know that this early in the bike I should have babied it, but I took it up to 65mph and I would say that is not near red line, but like I've read on here or another forum, i would need more air flow and fuel to go faster. But, I don't really want to go faster, maybe just get lower RPM and fuel economy.

Here is another question: wont using a higher flow air filter allow more debris to enter the engine, thus increasing wear? (especially in a dust environment) The reason I mention this is because a friend of mine has a Polaris 300 Quad and had interest in changing out the air filter on his but was advised not do to it because of increased dirt and stuff getting in motor.

So what is the bottom line here?