KT-735-3076 Running Rich/Poorly Under Load

Greetings, I have a KT-735-3076 engine in a Troy-Bilt Super Bronco XP with 128 hours. When it stalled out after hitting something and wouldn't start, I made the mistake of jumping it with a running vehicle. I replaced the battery and starter. Fortunately, the voltage regulator was OK. However, it's running, but not well under a load with the deck engaged. I cleaned out the fuel tank and line, replaced the fuel filter and spark plugs, and cleaned the carburetor which was fairly clean with no residues. It seems to run almost normally with no load and can zip around the yard with no problem. It runs poorly with the deck engaged and will stall in moderately high grass. If I had to guess, it seems like its running rich and it using a lot more fuel than normal. I did find what appears to be a spring or linkage missing from the carburetor (pics attached). I put a wire tie for now, but perhaps someone can tell me what part is missing or any other ideas as to what could be wrong? I'm not sure what else to do except replace the carburetor. 
 
Edit: I can't seem to attach pics

I can't seem to upload pics. They get to 100% and stop working. Here an imgur link to two photos: 
https://imgur.com/a/CNvAl3t
 
I checked the deck and there are no loose or wobbly spindles. It's not running quite right without the deck in operation, but has enough power to drive around at full speed. It really struggles to cut grass and wants to vibrate and stall out with the deck running.