My first post to this forum I have a stock 2001 400ex and am wanting to get into racing mx. I am looking into an exhaust, big gun or white bros.? Which would be better? I know the big gun is expensive, so I was wondering if it is that much better. I also am putting a K&N Filter on it. What else should I do to it? I am also getting my fenders cut down. I'm pretty new to this so all the help I can get would be great. Thanks a lot.