Magnaflow break in period

I recently had a mangaflow 16" muffler welded in to my 09 prerunner a few weeks ago. I LOVE the sound, very clean and not overly loud. I remember reading somewhere here on TW that there is a break in period for your exhaust and it will actually get louder eventually? Is there any truth to this?

I'm not against it being louder eventually I was just curious about how it will sound when fully broke in.

 

very doubtful unless its a fiber glash pack muffler it might get a little louder, but not much

 

Just got one put on today, the shop owner has been in business for 20 years, dealing with every kind of muffler you can think of

He told me my MagnaFlow will get a little louder after several hundred miles

 

I just got 1,000 miles on my Magnaflow and I would say it sounds a little better than when I first got it installed.

Just a tiny bit deeper, little less ricey at high RPM's.