| Airbox mod
I had the Sigma fim chip and airbox mod on my ST2, I have certainly felt the difference and the airbox induction noise is intoxicating.
Sigma have cut about 6 holes in the airbox all about the size of a fifty pence.
But beware I found Sigma expensive and a little lacking on customer care, they did not test the bike after the chip was fitted and the bike was not ridable on collection. | 
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