lawn mower bogs down

We have a LawnBoy silver series #10301. It has been repaired and tuned, but the repair person told us that the "throttle linkage is very brittle," (don't touch the slow/fast handle) and that they have set the power at about 3/4 to "spare" the plastic stress inside the unit on the engine itself. (?)
The motor sounds like it's dying, then recovers and revs up again. Not unlike a surge if using bad mixed gas.

I need to know what part to look for and where to order? The repair shop is not reachable for the rest of the summer but if I have the part, a neighbor can fix it.

Thanks

I wish I knew what he was talking about, the throttle control on the handle or lever on the carb. Both are fairly cheap and easy to repair. Did he say anything else?

Lawn Boy. Has the thin plastic vertical air vane governor and the real tricky spring that controls the throttle. Real easy to mess this stuff up when working on the carb if the wrench guy isn't up on the Lawn Boys. Don't ask me how I know this........ OP probably needs a new governor blade and spring, installed correctly and adjusted.