(2003) Luton T350/125 - NO POWER on inclines or Hills

[turbo boots]

Hi Guys - its turbo boots here from Falmouth in Cornwall "not so turbo at the moment" as my van has no power on inclines or hills, I first fitted a new air & fuel filter, removed the turbo, intercooler, EGR, TMAP & All hoses, cleaned/inspected everything = OK, In desperation I bought another van (same (T350/125) that was an MOT failure but drove good and swopped the bits - still No POWER, I am losing the fight against time on this one ..... and would really appreciate some knowledgeable help. my next try will be the valve that opens the wastegate and perhaps injectors?