Loss of power

When I'm driving and I shift into higher gear and I'm climbing uphill my reduce power light comes on and it dramatically loses power. The last time I checked underneath the hood it was the throttle (the butterfly) that was stuck closed not open why is it doing this. So I cleaned out all the carbon that was in there cuz it was really black and it's been running just fine since I made the move/trip to washington now about 3 or 4 months ago. Now all of a sudden it's starting to do it again after I made a trip back home to Montana and then back to Washington. And it only does it when I'm increasing speed, accelerating quickly, or hen using Cruse control on steep incline. Then all sudden it'll just loss power the light will pop on and it dramatically drops in speed but it doesn't die. It'll gradually increases and get back up to speed but it takes a very long time. And the reduced power light doesn't go off until I stop the car and turn it off and turn it back on. Sometimes I have to do that a couple times if I don't let it sit for a second before I restart it.