I will soon be getting a 2004 yfz450 with just nerf bars and I have a few questions. I am going to get the Sparks Racing pipe with the Big Core option. What exactly is the Big Core option and what does it do for you and is it worth $99.95? Also what kind of setup is the air filter and airbox lid? Like do I just buy a filter, outerwear and I am done? I will be running without my airbox lid. Do I have to buy some kind of converter peice so it fits in there good and everything? Please help with any experience and knowledge you have.