Occasionally I get a thunk sound, when starting with a load.
Almost sounds like fuel surging to the back of the tank?

Also, I get a chatter in the clutch when trying to get the truck up on leveling blocks ( truck camper).
Could they be related.

I think the clutch chatter could be due to the"no stall feature of the IP" ??????

Do any of the power Modules defeat the "no stall feature"

 

You might check you U-joints and rear axle components... (Thunk sound)

Clutch chatter is a sign that you've got hot spots in the flywheel... You might be looking for a new clutch soon...

As for defeating the no stall feature... NO... As far as I know it part of the injection system / Governor...