Black smoke

Hi,
Did an oil change on the sv yesterday and have since noticed that I'm getting a bit of black smoke out of the exhaust when I open it up (I have a renegade twin system on it and it comes out of the left can (rear cyclinder) although the two are joined by a little balancer pipe in the exhaust) It had it a bit before the oil change but unsure as to why?
The bike gets about 100 miles from full tank to the light (most i've seen is 112) which I worked out at about 32mpg which to me seems quite shocking. It's also used a little oil in the 1000 miles i've done on it, about half the sight window? is that anything to worry about?
When I took it apart and did the TRE mod I took the airbox off and gave that little breather spunge clean and it was absolutely drenched in oil.. is that anything to worry about?
Gunna put some Avon Storms on it this week aswell... o the fun....

If the bike is running rich (which it sounds it is) then it will be washing the bores of oil.

This will increase oil consumption and engine wear.

Are you sure the chokes are disengaging properly?

How do I check the plungers? I had a look the other week and relubed everything but all looked fine... bar the fact that the carbs have been tinkered with before by the looks of things.