My bike currently has the areap slip on mounted, and I've been trimming the fuel but haven't been to the dyno yet. Actually I have found a dyno I can purchase and I'm mulling it over... it's a good bit of coin, but I wouldn't have to rely on seting up dyno time anymore, so there is that.
Anyways, it's hard to accurately predict what might happen when "this" part stacks on "that" part.
To be honest, I was floored that my bike gained 14 hp with the stock exhaust. Floored to the point that we did several runs showing that gain, then I reflashed my stock map back in and got the 126-128 hp runs, then flashed the ECU back to my flash and back came the 142 hp. So with that in mind it kind of threw off my idea of "reasonable expectations".
I was back to the dyno with 2 other concours owners 3 weeks ago. One has a pipe I built with the stock pipe diameter header pipes with a 2 bros slip on. The other has a full area p system. The bike with the pipe I built had incredible low end torque even stronger than the area p system, but from 6000 up the area P system was considerably stronger. The bike with the small tube peaked at 146 and the AreaP bike peaked at 157. These are SAE corrected #, same as my 142 hp.
So with those #'s in mind, and IF the stock muffler is more of an impediment to power production than the pipe diameter or the CATS in the stock header then I think it's possible for a flashed bike with a slip on to get to that mid 140's area... 145, 146, 147, right in there. If it doesn't get any more than the 142 I already have, then we're at the point of realizing the peak power with the stock header.
So far with the slip on I can say the bike is fast. It was fast before, too. It's so linear it masks the rate at which it accelerates from low rpm so the butt dyno is less effective. I do feel a subtle climb in power at 5000 rpm that I didn't feel with the stock muffler. Subtle but noticeable none the less. This could be a good sign. Still, I need dyno data, which I will probably have within a couple weeks, and then after that the area P full system goes on, though I doubt it will stay; I'm really liking the quiet / fast and don't need to be alerting the men in blue that there's an ICBM tearing up the roads in their area of responsibility
In closing I do want to say this - Guys put on slip ons almost as soon as they buy the bike. 4-500.00 $. Sure there are some weight savings, about 14 lbs, and probably some extra power to be gained, but it absolutely won't achieve the all rpm power gained with my flash. Not comparable. In my mind, putting on a slip on first and then mulling over getting the flash is a bit backwards, because the flash is the obvious bang for the buck winner in that contest. Steve