2011 Focus 1.6 Tdci Boost problem

Hi Guys  I've always looked up the problems on Google and have always found the solutions until now. I bought a mk2.5 focus a couple of months ago. The car it self is a high Miler (178k) but is over was decent. The issue I'm having is that the car is very slow and does not pick up uphill or on the motorway.  As soon as i bought it I had a full service and major work done. (fuel filter air filter, Castrol oil, injector rings, timing belt, water pump) The dpf pressure sensor light was on so I changed 3 sensors, dpf pressure sensor, mass air and map. The light remained on so took it to a dpf specialist who told me the dpf had already been deleted and the light should not be on. He told me to get the car mapped as that might of been the issue. Once I took it to the mappers they took ecu out and confirmed it has already been mapped (same software as theirs) they then unplugged the dpf pressure sensor and light has now gone off. All this made no difference to the car. It drives well in town but response from the accelerator is intermittent (sometimes there power sometimes there's none) The car loses boost uphill all the time. If I switch of and on the boost comes back but only for a short period. Today I took it to a focus specialist and asked them to look for boost leaks and test boost pressure solenoid (AJ Automotive in Leeds) they basically did Jack and wasted my time. They went on about forscan did not pick up any faults, claimed they tested the car looked everywhere and couldn't find the issue. (Car was still parked in the same position I left it in) Anyway has anyone had this problem or know what it could be. My money is on the solenoid but I've had enough of mechanics trying to second guess and fobbing me off. Thanks