I thought my S4RS was pretty bad at 27-32, depending on how gently I rode it...never twisted it's tail very hard or very long. Dude who sold it to me said that when the fuel light comes on, you have 27 miles.
I flew out to Utah to look at it and hear it run, negotiated a deal and paid for it, (fuel light was on), and had it shipped to me.
When it got here the fuel light was on, but I had no idea for how long. So I rode it to the gas station, about 1.2 miles away. Made it 1.1 miles.
But that bike had probably had twice the HP of the S2R1000, so your fueling is really off, I think. There is a somewhat antiquated but still fairly accurate formula that says a reasonably efficient engine consumes approx 1/2 lb of fuel per hour per horsepower. You can do the math from there. So either your S2R1000 is putting out 200 HP or it is seriously mis-fueled. With that large a discrepancy, should not be that hard to figure out.
My 800cc S2R got 45 mpg or so, my S2R1000...never got it put together well enough to put a full tank through it. But I'm thinking that 40-ish should be reasonable.
Aftermarket pipe (no cat)? Should smell like a 1960s musclecar. My 996 and S4RS (as well as my current Multistrada 1200S) would all run me out of the garage after 30 sec of running. All had cat delete, Termi exhaust, probably mapped. All run great but all consume fuel in the area of 30 mpg...Multistrada can do (barely) 40 on extended highway trips with judicious throttle management, but is just as bad around town.
Running 20 mpg rich, should be spitting raw fuel out the exhaust and smell like the Exxon Valdez.