We have a dyno in uni and every car that goes on it makes what it should or roughly what we have calculated. VW lupo stats 65bhp standard and on our dyno it makes 60-67bhp standard. Few people have done project work on it and calculated a rough idea of what power output it should achieve and its near enough bang on, give or take few bhp. Test after test after it makes what it should.
I know no two dynos will give the same car the same readings but if the test procedures are carried out correctly there no reason why they shouldnt be two far apart. AMD quote roughly 265bhp from a remap so on any dyno it should make roughly that, may make 250-255 one day or 260-265 another but 230 (didnt someone get 226 from a remap also) thats a joke to me. Either the car not running as it should (which is likely the reason) or test procedures aint accurate IMO.