I recently had my 80 series muffler installed, but it sounds weak at WOT.. I have a gutted cat on the car & no headers..

Is the gutted cat causing the poor sound of my exhaust? I read a couple posts that the flowmasters sound bad with a gutted cat, but looking for a couple more opinions..

Will a hi-flow cat help my sound or will a set of headers be my best solution..

Help Please !!!!

 

that muffler takes a couple weeks to start sounding good and deep.