to the right of the operator seat is a boom up speed increase boom down speed decrease adjustment. How does it work and what does it connect to? It looks like a throttle adjust cable but it's seized. My boom up is pretty slow. I'm hoping my speed can be adjusted faster,
Not exactly correct. It only permits adjustment of boom down speed, not up. From the manual "Controls boom lowering speed - can be set to match application." An Operation & Maintenance Manual might be of help to you. Here's a used one for $20 - 225 Manual