The cops were genuinely surprised that they pulled someone over for blaring racing sounds. I get that the noise would be alarming and would make you suspicious, but don't you think the cops would be able to see just how slowly the guys were going? I guess checking the old sped-o-meter is a little too much to ask of a cop when he's busy checking out the hot flag girl.
In the end, the racers really did get the last laugh as they sent the cops home with nothing but a cop-block. Nice work, team.