Noise muffler-but new

I had a new muffler installed on my 2001 Regal because it sounded loud. I also had a catalytic converter replaced by the dealer because the car was missing when I accelerated. The converter took care of the missing or poor power. I also had the whole muffler system replaced. I also put new tires on the rear because I thought that might be the problem.

I am still getting a loud sound out of my muffler. Could a new muffler from Muffler Man go bad within a month? The faster I go the louder the sound. I have a hard time hearing the radio when I go past 50 miles per hour.

Could the catalytic converter be bad? I have run out reasons of the sound out of the new muffler.

When the whole exhaust system was replaced did you keep the OE resonator in place or delete it? Look underneath the car and see if the resonator is there between the CAT converter and muffler.

When the whole exhaust system was replaced did you keep the OE resonator in place or delete it? Look underneath the car and see if the resonator is there between the CAT converter and muffler.

Yes I had a new one put on the car, but still sounds like a bad muffler. Although it is only 1 month old sounds terrible. I took it back once and they sad it was not the muffler. Replace the resonator still have the sound. Replace cati converter, still have the sound. Put on new tires thinking this might help and still get the sound.

Any suggestions?