A note about volume increase with towing...
I had a beafy flowmaster installed a few months ago. I don't know why I waited so long. Not so loud that it gets annoying, but not so quite so all you here is the engine. I've had several compliments on the sound. The only way to sum it up is to say it sounds like it should.
Anyway... I tow a 5k lb boat around 40 miles (ea way) every weekend. There is absolutely a difference... I might say around a 40% increase in volume. It is tollerable for a 40 mile distance... maybe even 100 miles. I pretty much forget about the increased loudness. I'd say if it were another 20% louder, I don't think I could forget about it.
Would I change anything??? No way.