My K6 Vee does around 45mpg if I short shift and keep revs around 4000rpm, In top gear that's 70mph .
However, if I want some fun mpg is reduced to around 35mpg. I have a PCIII with a custom map , foam filter , titanium akrapovics , secondaries and clean air removed.
From what I can remember when my Vee was stock the mpg wasn't much better .