| Bradders,
This is one that has been talked about alot with classic bikes, not sure on facts and figures, but basically at top speeds for prolonged periods a fairing helps, but without a fiaring there is less weight and therefore the bike picks up quicker out of the corner and so long as the straight isn't massive will not have much of a difference. Some of the old guys used to take the fairings off for short circuits, and put on for long ones and road circuits.
I fell off a few years ago at Snetterton, and had to junk the fairing, but did lap any slower.
Also I find my DD bike with only the nose cone does not get effected by side winds as much as having the full fairing.
Not very technical, but my experiance
Steve | 
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