Sounds great! F150 5.4L
Upgraded from a single outlet Super 40 muffler and I can tell you the dual system sounds much better. It's not overbearingly loud but still has a great rumble. MPG gains are very slight but throttle response is definitely improved. I would recommend getting 3.5 or 4 inch tips though...the 3x12 ones included with this system are a little small at least for my taste.
Well, it's been over a week since I had my exhaust installed and I think it's work very well, to say the least. The sound is awesome with just enough rumble to turn a few heads! Would recommend this system to others, for sure. Now, if I can only find a cold air system that's CARB legal?