I was given a K&N air filter kit for my 04 kfx 400. It is a Mod Quad K&N air filter, sleeve and adapter. I took a quick look and will have to remove the air box, cut up the stock lid, drill holes and install the adapter plate. It's running just fine now with the stock jetting and exhaust. I don't plan on changing the exhaust now and debating on whether to install the air filter or not. I'd like to install it, but not if I have to mess around with the jets and carb. Would it be pointless to install without doing a full exhaust upgrade and jetting? Should I just leave as is. I don't race and just trail ride, not really getting into full throttle or higher gears too often. Any thoughts? Should I leave everything as is until I get the exhaust?