First off, THANKS in advance! It's been almost a year since I've needed to post any questions here. Thats a good thing though, my 450 has performed flawless. Now however, it has just started to shut-off over the occsional jump. Not every time just once or twice during the day of riding about 4 or 5 20 minute sessions. But...when it does decide to do this, well lets just say I've dropped a few "F" bombs as I kissed the front fender. I think it's happening on some of the steeper jump faces, where you'd chop the throttle to bring the front end down? Also it's blubbering when the throttle is cracked open quickly. My thought is it might be the airscrew. It also has been "lean popping" during deceleration. The bike is stone stock. I'm a little intimidated by the 4 stroke (first ever 4 sroke) I've not messed with anything, including jetting. I'll probably try and get a new exhaust before our next MX season fires up here in September. As far as pipes, I'm considering FMF cause I can get a deal on one, DR D or TA. Any thoughts? Thanks Again!