L10 Cummins Throttle hang

So I have this 1990 L9000 with an L10 PT pump with a Model 404 Jake, and it starts and runs great. The problem comes when you ever so slightly blip the throttle it will ramp up to 1550-1700rpm, and will increase from there until high idle limit. ~2200rpm. To bring it down from this high speed the throttle must be hit full sharply and let off. There are no linkages that are seized, and customer claims that pump was rebuilt sometime ago. The return does not seem to be plugged and there are no electronics on this unit. I am at a loss. I will upload a YouTube video soon and post the link here.



Thank you in advance,

Dion

L10 Cummins Throttle hang