Hi!
Being the Swedish MVVS distributer since 1992 I can say that MVVS engines doesn't need any lengthy running in time, just run a tank on the ground and then set the carb...and go flying. Fly it a little rich leaning it out tank by tank for the next 5-10 tanks.
When you can't give power without the engine quiting from half throttle, the idle needle has to be set. It is either set to rich or too lean.
It the engine stops instantly when you give power ...the idle needle is set to lean.
If on the other hand the engine blubbers and spits fuel ...the engine is running too rich.

The new MVVS carb is a wast improvement over the old one, so if you have the old carb with a idle needle with a thick blunt tip, I recommend getting the new carb or either get the new idle needle kit that is a replacement for older carbs.
Regards!
Jan K
Airracing products
http://hem.passagen.se/airracing