Really nothing, becuz all a resnator is, is a straight thru muffler with 2 outlets. For example, the race series Magnaflows have a straight thru design just like the Magnaflow resanators. The only difference is, is that the race series mufflers have tips, and the resanators have 2 outlets for piping.

Failure is simply the opportunity to begin again, this time more intelligently.