When discussing Valkyrie fuel mileage everyone has a different opinion, and some lie a little. Every opinion is based primarily on personal experience and is at least a little bit wrong (including this one).
Interstates do not always get better mileage than do standards. When they do it's likely due to the Interstate ICM. I doubt the Interstate carb springs actually improve fuel mileage, but they will give you a quicker response.
I seriously doubt that the wind management of the Istate's fairing can make up for the additional weight.
Standards and Tourers come in too many different configurations to be limped together. Windscreen or not; slope of the screen; weight and bags; weight of the rider; tires; tires and oil.
The 3000 RPM myth is just that. There is a line, but it's not 3000. Mine on my Standard tends to be around 3800. I am running a Dyna 3000 ICM with a rather aggressive curve and that could make mine different than some.
My Standard gets better fuel mileage than my Interstate. In fairness, my current Interstate gets the worst mileage of any Valkyrie I've ridden. My wife's Standard gets better mileage than my Standard and it irks me to no end,
They're all different. One thing is consistent. They all get more miles from the same volume of fuel at lower speeds and they all get less at higher speeds.
YMMV, but then everyone's does. 
Willow now that's the most truthful post I've read yet!
Are you sure you want to make such a definite pronouncement about it? (:
Seriously, he's right. To some extent. Sometimes. (There, I hedged)
From talking to different folks, I have come to conclude that different Valkyries seem to get different values for mpg, but lots of factors can go into that, such as riding style, tuning, and some esoteric "not all Valkyries are created equal" factor.
To add to the confusion, different Valkyrie riders report their mileage in different ways:
1) Some folks say they are "out of fuel" when they hit reserve.
2) Some folks say they are "out of fuel" when they think they'll hit reserve soon.
3) Some folks say they are "out of fuel" when they're pushing.
To further add confusion, not all odometers are reading the same amount, I believe.
As Ricky D said, the proper way to calculate it is actual fuel required to fill up, over multiple fillups averaged over time. The longer the average, the less that small effects such as wind speed/direction, hills, how close you got to the top of the tank, etc. will factor into the calculation. Of course, riding style will be somewhat constant, other than highway vs. in town. Keep track of that last factor, and try to keep it constant, and you'll get a good value for that condition.
PS: I've agreed with Ricky D twice this month. I'm over my quota for the year.
