factory flaw in a muffler?

follow up: mufflers are OK. However my motor seems to hate the factory manifolds dispite the porting work done by Gesslers. Cant do it "this" year but the tti step headers are a must for a winter project. Might as well install the X pipe while we're under there.
As soon as the new race converter is installed the car is going up on a chassis dyno and we will see for sure exactly how much the factory iron is hurting.