I have a stock 03 XR 250, and I was wondering if it is worth it to replace the exhaust. Would I get better response with a new exhaust than to replace the baffle? If I do get a new exhaust system, should I just get a slip on or new headers too? Also, I have heard something about removing the air box cover? Did I hear right? Is this just the cover underneath the seat? Can't water get in if you take this off? Lastly, should I rejet if I get new exhaust? Thanks!!