Find a new mechanic, any change in intake/exhaust goes hand in hand with jetting. These machines come lean from the factory and by pulling even 1 baffle you made the engine even more lean. The more you change the more the jets change. At the very least you probably need a larger pilot now and probably a slightly larger main. You also need to adjust the mixture screws for sure.

EDIT: Just noticed you are from the UK, are stock bikes jetted any differenly from the factory for the UK vs. the US? If the jets are larger stock over there you may just need to adjust the mixture screws. (I doubt it but the thought just popped in my head)

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