The new carburetor could be the issue if it was from Amazon. It is likely not jetted correctly. Do not mess with the governor. The governor only keeps the engine from trying to run wide open and blow itself apart. It is a speed limiting device and it has no effect on what you are experiencing.
In parts tree, this carburetor shows to have regular altitude jets (leaner) and also high-altitude jets (richer). You likely need the high-altitude ones