True...never got it rolling roaded. Definate power gains but how much i couldnt say, performance gain is mostly 5k plus but its definantly smoother all across the rev range. Ive lived with it for a month now. I like it but as you were interested in fuel comsumption its dropped by approx. 2 or 3 mpg in normal use (similar driving and conditions), but on the motorway at 80mph its dropped about 4 or 5 mpg.
Dropped as in got worse.
Its worth noting though that i do drive quite heartily...
So if your doing it for economy.....i wouldnt, but if you want more go then id say a definate yes.