i use to do that to peoples cars years ago. At the local prank store they have these clips you put on the back of someone's muffler. When they take off there car makes that sound, then the person driving thinks there car is f'ed up and takes it to the shop.
hope that doesnt hit in michigan.. i hate those grapefruit shooters some morons have on the backs of there civic!
"man my car is fast just listen to how loud my muffler is!"....IDIOTS!.....
dont they know you can make your car sound loud just my punching your fist through the muffler?