That used to be the standard fix for noise tickets. You have to take care that the stuff stays put though. A friend of mine learned too late that you need to drill a small hole in the pipe and drop a nail in behind the steel wool. The inspector was just about to sign that his car had been fixed and, on a whim, asked that he step on the gas one more time. That was enough to blast a steel wool pad out into his shins.
Between the bit patch of carbon on his pants and the damage to his leg, he was not happy at all.
