Engine Malfunction

[godimgood99]

Ok I keep going into limp mode I can go 6weeks with no problem but tonight it returned engine malfunction after turning it on driving a bit more about 20 times I gave up called the aa he plugged the computer in he said you ave under boost on your turbo charger he cleared the code power came back no as much as he should have but it was better than after 10miles back into limp mod and engine malefaction this time no codes though Evan when the computer was plugged in and engine malefaction was showing still nothing so anyway I got towed home an when we got back the power was back again any help would b appreciated before I o and get ripped off in the morning oh and it's a 1.8duratech diesel