My 03 cooper s has an aftermarket exhaust no idea what kind I bought it that way it drones like crazy will a glass pack used as a resonator stop the drone

 

That's basically what they are.
But I'd guess the factory mufflers (like most newer ones) have a stainless steel filler rather than fiberglass. The main difference, the fiberglass will deteriorate faster than the stainless will, requiring placement sooner. Should last 30,000 miles before it needs to be replaced. But as noted, most newer packed mufflers have changed to the stainless packing.

Mike