you may find that people tend to have more to say or post slagging of dynos(i dont just mean duncs) when their car hasnt made the power they hoped or expected it would....for all the bad comments, there will be plenty of good feedback too, have seen him run up plenty of cars that have made the correct/expected power, or the cars that have had issues/problems identified when running up which once sorted were very happy with the service...
as stewartyboy says, there are lots of different factors which can affect the run and it is a guide, however from what im led to believe dyno dynamics are supposed to be 1 of the top rolling roads....
are horsepower figures that important?or just for pub talk...ive been there where you get fixated on a "magic number" but at the end of the day all that really matters is how it goes on the road.....i remember going back a while now having a blast with a guy who was shouting that his car was 450bhp, it had been at dastek, my car had been on steve simpsons dyno dynamics and made 386bhp and i smoked him.....so his graph was worth about 2 balloons and a blow at the rag mans trumpet