This symptom coincided with the new injection pump being installed? Any other recent work?
Just thinking about it logically, high rpm requires extra fuel AND air. Where could extra air be supplied from? Barometric compensator, warm up device, brake booster, other? What about extra fuel? Cold start valve, leaky injectors, fuel injection pump richness adjustment, other? You may want to recheck linkage adjustment. Check plugs for rich/lean condition to see if extra air or fuel is bigger problem.