Here's a link to the insert I was talking about earlier, not cheap, but well made (stainless) & they do mellow it out by a Db or three.

http://store.summitracing.com/egnsea...115+4294865320

Vortex cone inserts from Dynatech easily install near the exit of the header collector or muffler outlet to reflect and dissipate sound energy, reducing the decibel level. Because the open area of the cones is greater than the area of the collector or exhaust pipe, there's no significant backpressure, so you reduce noise with little or no power loss. The cones are made from T-304 stainless steel and weigh less than 1/2 lb. each.