Sounds as if you've got up thrust in the motor mounting.
That would be highly unusual for an Extreme-Flight airframe but none the less
that is something you should check out .

I've flown a number of examples of that type which were simply dead on so something is amiss.
Has the airplane been damaged or did you buy it from someone else ?

This is a Futaba site so this message won't last long as I'm not Futaba.
They can give you the how to's for mixes but that isn't your problem nor is it the correct solution IMO.