Matt, Just because you go faster without the airbox, doesn't mean you are running rich...A lean moped will go very fast, until you seize your engine. Have you done a plug chop? What color is it. If it isn't really black, then you aren't running rich. First things first... do a plug chop...Get a new plug in there, and get your ped warmed up. Then ride it about a quarter mile at full throttle. Once you are at top speed for a little while, hit the kill switch with your thumb. It is important that you hit the kill switch while your bike is at full throttle. Park it, then take out the plug and check the color of the ceramic part underneath the contact. You can let it cool off if you want to, but I never do. Once you do a chop; If the color is really dark, first you should check to see if your airfilter, inside the box is really dirty. You can tell because it will look black on the side that faces the hole in the airbox. This happens a lot. At any rate, take it out and clean it with brake cleaner, and then see if the ped runs any faster. You may have to cut along the edge of your airbox with a razor to get it to pop open, because they are usually sealed...but don't worry, because they are hinged at the bottom and close right back up, even after you have broken the rubber seal....they were meant to be opened. Do a plug chop after that and post back. I bet this is your problem. If you still aren't satisfyed, that is when you start modifying the airbox and buying bigger jets.