I recently bought a 12 yz250f. It appears to have the 450 muffler on it. It's much shorter than my 10 and the diameter of the exhaust is only 28mm. I'm racing this weekend and need to use the 12 as I recently damaged my 10 and need to be below 94 db. I swapped mufflers which has the db dawg in it as well. Now it seems to bobble around 3/4 throttle. When I powering up strong it's ok but just putting around its got the bobble. It almost feel like a starving for fuel condition but the longer more restricted pipe would/should make it richer I anything, I would think. Am I correct in this assumption?