dw8b stiff throttle hesitancy link

[finny]

ive had the berlingo 1.9d dw8b for 2 years with a slight hesitancy problem around 2500-2800 rpm and have also in that time replaced 4 throttle cables, got used to it but then the hesitancy went away and with it the stiff cable, but its come back this week, basically with the engine off the cable is fine but when running it gets stiffer, i did read once about some sort of rod in or around the pump getting sticky but cant find the info now, one other thing that could be linked approx once every 6 months the engine makes a nasty rattle which is sorted out by turning it off and back on which i believe resets a solenoid on the pump timing, any ideas?, thanks