657 HP with a 509 cam? Not by me!

My assumption is not an idiot tuning or driving the car. Any moron can make a car slower and make the math not work. The assumption on my part is they do have a fairly well scienced out package. I'd even go as far as to say there are more dyno'd engines running slower numbers than the math says because they don't actually make that power, than ones that actually do make their numbers but it's all wasted on a poor chassi or driver.
Dyno results can be manipulated on all kinds of levels and are rarely an accurate simulator of what a specific engine will do running in a specific car. Chassis dynos have the potential to be a little more realistic but again they can be manipulated too. And yet dyno numbers are always posted as if they have some meaning beyond that engine on that day in that dyno room with that operator.