yesterday, i put a shorty on my cr250. i didn't have to re-jet or anything. it did make a slight but noticeable increase in bottom and mid performance. it may be a tad louder than the DEP that was on it but not so much that it's bothersome. i am very pleased with it.
i was the only two-stroke on the gate last night. and probably the only bike that the people in the bleachers couldn't hear.