I rarely notice the sound of the MDS, it goes quiet. Sometimes kicking in or out of mds you can hear it a little more but thats about it. This is with the 18", and the exhaust is plenty loud when you want it to be but quiet on the highway - perfect IMO.

 

i have 18" on my truck and i love it! when you step on the go pedal everybody knows, and when you are just cruizen around its nice and mellow.

 

Yes, I have the 14 with about 9K on the muffler.