The governor is basically a spark timing advancer, at 2000 rpm's it starts to function (advance spark) partially and at around 4000 to 5000 rpm's its supposed to be in the fully advanced position. A little gap on the spring resting terminals, worn springs, or an out of shape cam lobe on the advancer will produce a miss in between quarter throttle to full throttle.
Fortunately, the springs, cam lobe, and the scissor like parts are all replaceable, meaning if one part is worn it isn't necessary for you to replace the entire assembly, replacing the worn part with a good working one will solve the issue. Reason I explain this is because the entire governor assembly will cost you an arm, whereas replacing the damaged part will definitely save you plenty.
The saleemi shop will do what you can yourself, may or may not rip you off of price as well as part integrity, so I would rather suggest you to get the part and have the mechanic fix it right up.