put a big zip-ty on the axle of his car or truck, preferabley in line with the muffler, as he goes down the road it sounds like the valves tapping, but when he stops to listen it stops, it'll drive him nuts tryin to figure it out, i actually had someone take their car to the dealers to have it looked at, luckily they thought it was so funny they didnt charge him nuthin
i also had a guy down the road who gave me some trouble, i went to the sporting goods store and got some skunk scent in a little bottle, it's used to cover your smell while hunting or trapping, i took a syriinge(hypodermic needle) full down the road late at night, stuck it thru the rubber gasket around his window, and unloaded the whole thing into his new car, i saw it go up the road on a flatbed, never to be seen again, fixed his ass, didnt i ???