Running rich?

I've put about a thousand miles on my 05 ST1300. I picked up a set of TwoBros pipes that were a little loud so I added the power tips. In 500 miles they already look sooty. I've got a new air filter and getting 44 mpg. One thing it could be is I had to replace the thermostat last week so that may have something to do with it. Just wondering if this is normal or should it burn clean? Thanks

I believe the converters are in the stock mufflers/exhaust pipes, so there may be more "emissions" with the aftermarket exhaust.
If you are running normal three bars coolant temp and no sensor issues the system should never run "rich" except during warm up and cold temps. If you do a lot of short trips it takes quite a bit more fuel. The ST1300 likes it warm/hot.

If you are getting 44 mpg then I wouldn't sweat it. I'd say you're doing pretty good. I average around 40-42 with the crap gas we have around here. Also, the fuel system in the ST1300 is a "closed loop" so it monitors the o2 content of the exhaust gasses and adjust the fueling on the fly so it should automagically adjust for the freer breathing from the less restrictive cans.