So, first figures..... 30mpg. But I was very foot heavy on the way down, about 70mph up and down hills all the way

that's 3500rpm+

also had a problem of it feeling a bit sluggish after arriving in Cornwall, followed by on this drive home, popping off boost pipes. The joiners don't have swaged ends, but I should have the bits waiting at home to fix this, thinking I was loosing some boost through bad joints before they started popping off. Tightened them real good and engine is back to being perky again. I don't know if this would affect mpg figures?????
So sticking to 60mph on the way home will hopefully improve the mpg. Need cruise control now though, as I can't stop driving fast......
It did 600km before I filled tank again, the aaz would only give me 500km
Oh, and these figures aren't using GPS, just the tripmeter. It certainly feels better than 30mpg as I filled up the tank 100km later than normal, and it still wasn't in the red.
Time is a drug. Too much of it kills you