Well since that question didn't go anywhere; I got the FBD exhaust and put it on Sat. I had a few problems (none of which were related to the kit) because my factory hangers were removed by whoever put the last set of pipes on the truck. All in all, it took about three hours and some head scraching.
It is sic. I wasn't really expecting much of a difference because I was already straight piped with duals. If I would have realized how much breathing room it needed I would have done this a month ago. It isn't much louder than before. But, the sound itself is quite different. Also I left the 3" section long and let it extend into the 4" by about a foot. I did this to allow it to act as something of a resonator and settle the exhaust pulses and tone somewhat. I'm not sure what it would have sounded like otherwise. But, the tone is pretty smooth. The turbo is a bit louder and either it is coming in sooner or I just couldn't hear it that early before. We'll see on the MPG improvement.
Great system - Thanks Gus