Yep, I spent a couple of grand tuning a 600 suzuki, made over 100hp at the back wheel. Thats 30hp and an extra 2500rpm
They changed loads, cams, carbs (even different jets between carbs), timing gears, exhaust (TTS, very good people) what do you think they left well alone. Yep the airbox, changed the filter in it. But they will only remove the airbox with direct instruction.