Just traded in my son's bike and my YZcam/free mods 03WR250 for an 05 WR450. Son ran away to birth parent, different story. Anyway, what is this air induction system and what mods apply? Yamaha has done a number of nasty things to stop one from doing any performance mods. What's up with that? Here are the problems I discovered so far. The exhaust is internally restricted. Do what you want with the tip, it doesn't matter. There is a 1" hole going into the spark arrestor chamber. If you want airflow, get a new muffler. There is no fuel screw and the jetting section is ommitted from the manual. I tried to install a zipty screw and found a plug on the carb bowl. I checked the manual and cannot find the fuel screw in the parts breakout or the carb assembly section. I will remove the bowl tommorrow to verify this. How can you FINE tune/adjust the jetting up to 1/4 throttle? Does Yamaha expect us not to jet or does this new air injection system help with the mixture. What does this new air induction system do? It goes from the air box to the exhaust and also just after the carb. I thought it was just to dulute the exhaust for CA emissions green sticker. Thanks CA, our air is to thin in CO and we need all the airflow we can get. Could this somehow mechanically adjust jetting by adding air to the mixture after the carb? It is only mechanical not electronic. Does the grey wire mod apply? There seems to be a rev limitation even when in 5th gear wide open. Wich brings me to the throttle stop. The throttle seems to move a lot. I will open the throttle section of the carb and verify if the stop needs to be cut. However, currently the bike seems to cut out or chug just before I reach wide open throttle. Must be cdi rev limiting. Lastly, this is an off road bike. What's up with the lights on all the time? Need to sell a few bulbs? A switch will fix that in a hurry. I like the bike. It has lots of torque at the low end <1/4 throttle. More powerful than the wr 250. However, in a straight away, mid range and top end, the 250 would win since my WR250 could rev up. At 1/4 throttle the bike starts pushing against the muffler. I also like the 1st gear for short, technical control. It will be a great woods bike because of power delivery. I just wish it had more power to deliver from stock.