Wow, great info! I will be studying up on this. I am due to take in my machine for the 10 hour maintenence, and will ask my dealer about this stuff too. Thanks so much for the replies. I couldn't have asked for better info, now it is decision time. Looks like removing the airbox lid, adding an aftermarket filter, outerwear and a jet kit is the first step, then a pipe later. Sounds like it will be easier to get jetting right when I add the pipe if I get the jet kit, and $45 isn't so bad.
thanks again.

4Hacks
400ex, bone stock.