There is a 5 per cent variance between dynos--some give higher results, some more conservative results. But as long as the system is set properly, you should get pretty accurate numbers. The guy that ran the dyno on my engine told me that their system gave conservative results, and that magazines used systems that gave higher readings. He told me a customer purchased an engine from Hendrick for circle track racing, and their dyno results showed 35 less hp than the dyno at Hendrick. It's all relative.