If the egr valve has been sticking open hence the intake system air leak detected code the DPF will be overloaded with soot. If you neighbour can get hold of a Tech2 get him to see what the soot content is. It may say 109% full etc also the kpa reading will be high. Try and get him to do a static regen and see if this helps but if its really blocked you may split the rubber/plastic hose that goes to the dpf differential pressure sensor.