I agree you should check the carb diaphram. A member here just replaced the carb diaphram and cured symptoms similar to yours.
In addition, I would advise you to take the variator off and look at the triangular slide pieces, the sliders themselves, the boss, and the bushing in the movable face. If any of these is worn badly your power will go down. There may be some noise and excess heat in the transmission case as a symptom. My sliders were ruined because of completely worn out boss and bushing.
I think some small or gentle groove in the pulley face is not too serious.
Check compression if none of the above cures the problem.