Extrapolating Beyond Reason: Statehood and the Gas Tax

There's been some discussion, probably less serious than it should be, about creating a new state out of Eastern Washington so that its residents wouldn't be subject to policies created primarily for the Puget Sound area. The only argument to be widely used against the split (or for it, in the view of some Westerners) is that Eastern Washington receives more money in transportation spending than it produces in gas taxes (and the numbers are still pretty close).

Quick Question: Are all of these dollars actually spent in the counties in question? Picture, for example, an entirely empty county that a road needs to pass through. Supplies and labor would have to be imported from neighboring counties, but would probably be attributed to the empty county, prompting idiotic questions like "there aren't even any people there, why are we giving them money?"

More importantly though, why do they stop at gas taxes? Gas taxes make up 6% or less of Washington State revenues. What about the other 94%?

Now, I'm pretty good at finding stuff on the internet, sometimes it even shocks people - but I couldn't find this critical information out there. My contact at the Census Bureau says the state doesn't even publish it. So where is the other 94% spent? I guess they just don't want us to know.