Dear don't go for after market carburetor of khyber because it will be used, i did repaired butterfly and jet valve but this is all wastage of money, this won't give you more then 10km average.
After installing mehran carburator i took my khyber to naran, babusar top, gilgit, hunza, hopper and khunjarab pass, and it didn't loosed pick on high ascend of chillas to babursar.
i never felt it under power. if you felt you still have an option to change the jet (but i prefer to keep new carburetor in genuine setting).