2. misunderstanding of the acronym I believe, DWB is Drive Without Brakes, you don't need to use the clutch for that.
Maybe you were thinking about coasting ?
What I did was shift early and try not to ride too fast.
On top of that you could go for a sprocket change (bigger front, smaller back) to have the engine spin slower for a given speed and have the engine under more load (which means more throttle hence less pumping loss)
Re-jetting is not gonna do wonders, they are quite lean to start with for emissions control.
Actually I recall reading about a BMW R100 that picked up a few mpg with "power" jetting.
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