I'm running the FMF Ti Powercore on my YZ450F. With the spark arrestor removed the bikes runs good. I ran the bike for the first time today with the spark arrestor in and it had a lot of low end hesitation. The hesitation would disappear when I got on the gas, but at a steady speed it would reappear. I'm not familiar with jetting, but it appears I may need to rejet. What can I do to smooth out the engine with the arrestor in, while protecting how it runs with it removed? Signed BAFFLED.