Well, on my new truck I've got Flowmaster 10 series without a resonater and they are VERY loud and the do drone some on the highway, but I like it, In 6th gear at 70mph they aren't bad, but when your going from redlight to redlight that's when the sound is really noticeble.

Back in highschool I had a 1990 F-150 with the (old) 5.0L V8, and I had Flowmaster 40series on it, and they were much more balanced than the 10 series...The Flowmaster 10 series are designed to be as loud as possible while still having an actual muffler on your vehicle. The 40series mufflers are still pretty loud, but compared to the 10's they are much less agressive.

Flowmaster 10's are designed to legaly **** off your neibors.

Flowmaster 40's are for the more considerate haha.

Of course there's the 50' series and so on and so fourth all of which give it a different sound or make it a little quiter.

Some people try and argue that Flowmaster mufflers aren't reliable, but I had them on my 1990 F-150 from 2003 to 2008 so 5 years of rain, snow and shine and when I traded that truck they didn't have a spot of rust on them.