i would check the brushes and to check do the following:
1. Remove the battery
2. Remove the holding plate that is underneath the battery (you have to un-attach it from the fuse/relay boxes first)
3. Next to the N-CVT dipstick is the electrical connector for the brushes. Disconnect this.
4. This electrical connector was plugged in to the brush holder, unbolt this panel. There are two bolts, top and bottom.
5. CAREFULLY remove this brush holder.
6. Check the brushes, they should not be worn down to the mark.
the clutch on the n-cvt is known as a powder clutch when you press the accelerator pedal a micro switch is pressed
and power is sent to the brushes which in turn magnetizes the powder which give you drive and vice versa
if the brushes are worn to the line or you cant see the line then this maybe why you have lost and then gained drive as the powder is turn from a magnetized state back to a powder state.
i believe that Delco alternator brushes are very similar and can be used in place of the originals i am sure an auto spark would fit them into the brush holder for you for a small charge
