E8: Throttle pump and staging
 

Having a bit of problems since I upgraded to 1600cc secondaries with stock 550cc primaries. Engine is a stock port REW with non sequential twins.
Problem happens at at part throttle and in vacuum. Car stutters and jerks when in that scenerio but don't see any erratic AFR's popping up, but if I floor it, it seems to be fine. Also on decel, it will jerk the odd time, sometimes violently. I've been street tuning it but am wondering if I should be looking at:
Richening/leaning the staging bar
Playing with the staging correction map
Throttle pumps

Thanks for saving me time