Yeah right - blue cars !! he he
I reckon the extra Kilowatts came from the energy permiating from the two good lookin blokes in the back seat at the time of the run....
Seriously, with your sticky tyres and the extra weight in the back, I reckon there was less slip against the Dyno hence the better results. (that sound like BS to me actually.)
Duncan , last time I ran there - I got 150rwrw with std boost and a cat back zorst - so a few extra PSI could make the 13rwkw diff, maybe ???