Dyno charts can be manipulated to show anything you want. In the very beginning of the article KB says the exhaust companies blame them for not seeing certain results and their goal was to prove exhaust does nothing. Therefore I don't believe one word they said. Track slips are the real tell-tale show of what mods do for you and there are millions of threads showing the gains from headers. And i can personally vouch for the gain made, especially above 3000rpms. And one other note, they didnt retune for the headers claiming that it would mess up the results, when in reality the perks of add exhaust upgrade is to allow you to be able to tune and add more air/fuel coming in with more timing since you are scavenging more gases out.