Has anyone noticed significant jetting changes when changing air filter brands? I have a cr250 and just recently replaced the stock air filter with a No Toil filter. The last 3 times riding I've had problems with my plug fouling. The only thing I've changed is the filter (still oil it the same). I don't have any leaner jets currently so I plan on putting the stock filter back on for my next ride to see if it fixes the problem. Just curious if all aftermarket filters cause jetting changes?