I have a 2007 XR650L I bought new last summer. It did quite a bit of popping on deceleration and of course felt quite corked up. I all I have tried so far is putting in a 165 main and adding the washer. That seemed to give it a little bit on response but it still pops. I am new at this forum and see all of the opinions. Does the Dyno jet kit actually have a different needle? Is this the way to go over trying to do some simple jetting changes? If I don't plan to upgrade the exhaust right away, is a jet kit still worth getting? I believe it makes a difference which jet kit you purchase depending on things you have done to the bike. It sounds like I need to do the smog block off kit and I do plan to get a foam air filter. What are my choices for an '07? Moose doesn't list a part number past '06. Last but not least, who makes fuel mixture screws for this bike?