UCANTCME says that hyperventilation can alter the results by as much as 10%. Any idiot who would intentionally cause themselves to hyperventilate in order to start their car should be arrested for reckless driving. Hyperventilating while driving can cause the driver to pass out from a carbon dioxide overdose.
Due to severe emphysema I hyperventilate on a regular basis, and it's neither fun nor funny. It's nothing to play around with, suggest, or even try, just to beat a machine.