Hey Everyone! I need some sage advice regarding my 00 WR400 and its jetting. I purchased this bike from a guy that took really good care of his bike, and the things runs really well, even a year later with me riding it, not a hiccup. When I picked it up, he had converted the bike to a MX machine. It is jetted to run with a YZ pipe, timed YZ, with all the free mods done to it. I sold off the YZ parts and converted it back to the true WR setup, using the stock pipe minus the tip. I run a downturned tip to help keep the noise down and also keep it free flowing. Still, pretty loud for the road, legal as it is. I have bought a K & N filter to help increase the breathing, and I also want to buy a GYTR insert from Yami to help quiet it down so more so I don't scare the crap out of the small children, forest animals and god fearing tree huggers where I ride. My questions are this. 1. If I add the K & N, is it going to make the engine too lean since it is jetted for a YZ setup? Bigger problem being, I ride offroad bikes well, don't know much about rich/lean setups and the innards of the carb/motor. 2. If I add the GYTR insert, is that going to cause me to foul/offset the jetting that is currently set? Will the K & N help offset that? I have ridden it for about 300 miles since I bought it, changing the oil every 4-5 rides. Going to get a valve adjustment next. Any ideas or guidance would be greatly appreciated. Cheers!