Wow your consumption is pretty good.
The best I can get on highway is 28mpg, I average around 24-25mpg
I had it to vw a few times with "nothing wrong", so I just live with it.
I found a thread on golfmk5 from memory, someone had the same consumption. Turned out to be a vacuum line behind the engine. My laptop crashed so never actually got to read the full thread. However I will try and find it.
I will hopefully install my boost gauge with in the next week. Then see if I'm loosing boost due to leak or if there is actually a problem.