My two cents on the subject of Dynomax mufflers is that over 20 years go I went with the longest “RV” stainless steel straight through Dynomax in the 2.5 inch diameter. Its price was lower than the heavier advertised performance SS Dynomax models, I suspect because RV owners pay more attention to value. As a single muffler it had a low deep tone with very little high frequency noise and cut backpressure to half that of the Walker Quietflow square case before it. I then bought the shortest stainless steel RV Dynomax as a “resonator exhaust pipe end” The resonator addition dropped the 1600 to 2000 rpm part throttle highway cruise sound level.

Mistakes I suspect I made back then:

I did not know how to “guest-i-mate” the effective length of exhaust pipe from main muffler to resonator to “fine tune” frequency range of noise.
I was not aware of what “T Stub pipes” could accomplish noise & frequency wise.
I did not have, or attempt to borrow, a dB meter with frequency range adjustment. (free Apps for that today)
I did not understand the pros & cons of changing the EGR tap point from exhaust manifold to way back somewhere behind cat con and/or muffler(s).

The stainless steel exterior of both main muffler and resonator still look great after all these years.