The bike gained more than 2 #'s Tq, more like 5# at 3500 rpm, which is very noticeable.
IMO the flies are to nanny the lower rpm power, but they aren't the impediment to power production that most think. For starters, the flies are a larger diameter than the actual throttle plates, so given any percentage of throttle opening, the flies at the same percentage allow more flow that then actual throttle plates. What folks aren't considering is reaction time from throttle input to achieving the secondary opening. They're fast, but not like the speed of light. also, I have experimented with a lot of early fly opening; flies out, and even cutting the flies. to much opening or flies out leaves a flatness / breathy feeling that slows throttle response. Very noticable if you're a tuner and know what to look for. I actually backed off of the fly opening in my flash to achieve the snappy throttle response it has. Y'all can argue / discuss / haggle it all you want; I'm telling you factually that to much fly opening or removing the flies is NOT the best way to go.
As far as slipons are concerned, I have no issue with them at all, but I am also a realist. The simple fact is that a slip on with a DBkiller / baffle in it probably flows less than the stock muffler, and that kills power. I know guys put on slipons for the weight savings and the look, but be careful and know what you're doing before you drop the coin.
JMO, Steve