Statesville? I'm next door in Hickory. I was involved in a hit & run in Statesville 2 days ago. Crazy people in Iredell county, lol.
As far as the Flows ..... I think they are a little different. I ran a regular 40 on a truck ..... then swapped out for the DeltaFlow. I think it's a tad quieter, but more rumbly. Supposedly (the guy at the exhaust shop told me) the Delta will free up a couple of horsies over the regular 40's. I couldn't tell a difference, though.
Delta series have "special technology" to quiet it down a little while cruising, but still have that "classic flowmaster sound", or at least according to Flowmaster. So yea, they're a little quieter. No hp difference as far as I know.