It is probably Sigma Performance that you're talking about. They did a bit of work on an ST4 which is Neil Spaldings own bike. You can read about it
HERE On an ST, and quite a lot of other Dukes, the airbox is quite restricted. If you look at a Ducati Performance airbox lid, it's not even a lid...it's just a frame that keeps the airfilter clipped into place. Taking the top off the lid gives loads more airbox volume and smooths out the torque curve, but as you'll read, Sigma decided not to leave the lid completely open so that the air filter didn't get soaked and to cut down on induction noise. Apparently they got another 4 bhp, but remember that's on a four valve ST4, you may not see the same gains on a two valve ST2.
Jools
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