David, I don’t know anything about that model, or MGs in general, but I agree re it showing too rich. Maybe clean the plugs, manually seat the choke in order to eliminate (or confirm) the choke as the culprit. Drive the car, pull the plugs and see what they look like. If they are still sooty, that would indicate carbs are set way too rich.  Is this a new development with your car(just started happening)? 

Steve - we held a Tech Session on this problem and discovered the choke cable was not properly adjusted.  Fixed that and then worked on the mixture - car was running rich.  Last report from David was that the car is running fantastic.  Hope to get a report about the plugs after a few more drives.

Great to hear - another beauty back on the road 

Follow-up from Part 2 of the session:

We discovered that the Adjusting Nut was screwed all the way in (full lean).  Note: one video online suggested the baseline setting for the adjusting nut was three full turns off the bottom.
The solution was to a) back the adjusting nut off one-half turn from the bottom and b) extend the Jet Needle a little bit more out of the Piston (decreasing fuel-air ratio).  The needle should not be bottomed out in the recess of the piston.  There may also be an indication line on the Jet Needle that should be flush with the bottom of the piston, at least that would be a baseline position.

All of this was facilitated by the ‘special’ SU carb tool (shown in photo).  Note: the angled version shown is necessary to fit in the tight space between the forward carb and the side of the MG T-series engine bay.  An SU wrench set is available from multiple sources for under $20.