Let me add...Even without the PTO engaged, at full throttle, it'll stumble also. If I pull the throttle back a little, it'll catch up and run fine. Even driving it around w/ out the PTO, sometimes it'll stumble.
Gents...I'm scratching my head here. My 729G2 Kubota Gas mower will not stay running right. I can start it and run it up, but once I engage the PTO, it'll start falling on it's face and start to spit and sputter. I'll turn PTO off, and it'll recover. It will sometimes catch up with the PTO...