CMax 1.0t engine issues

Hi all.

Having issues with my 2012(62) 1.0t ecoboost CMax - 85k miles currently. 

It's hard to explain but it almost feels like the car is putting itself into limp mode but I'm getting no warning lights or anything. It mostly seems to happen when on motorway or dual carriageway and you can feel something click over then I'm left with very little power until i turn the engine off then on again. I've even done this while the car is still moving and as soon as it restarts the problem goes away. Sometimes for 30 seconds, sometimes for the rest of my journey! 

I've had it into a garage twice now. The first time they failed the turbo as it was sticking when hot so its had a brand new turbo and i also had the annual servicing done at the same time. The issue was still there so it's been back in and they've diagnosed and replaced a faulty turbo boost pressure sensor. I've just picked it up tonight, taken it onto a dual carriageway and its immediately done it again. 

I had the clutch and flywheel replaced a couple of months ago so with that and the turbo I've sunk 2.5k into this car and I'm getting to the end of my patience with it now. If i wasn't in negative equity with a loan i took out to buy it I'd just sell it but if i do that it'll cost me thousands before i can even think about replacing it so for the time being I'm stuck with it. 

Sorry for the novel, and thanks in advance for any help you guys can offer!