Engine Malfunction, turbo cut-out 2.0tdci

Hi guys, new here and having some issues with my 2013 Focus 2.0 tdci.

A couple of days ago on my way to work I accelerated and as I got to around 55mph a warning message came up reading "Engine malfunction, service now" and it seemed as though the turbo cut-out, didnt lose all power and didnt seem enough of a drop in performance for me to consider "Limp mode" but there is certainly a very noticeable drop in pulling power whilst the warning message shows. The sudden drip in power is especially problematic on slip roads to join dual carriageway as the poor driver behind is not expecting me to slow down my rate of acceleration.

Turning the car off and starting up again cures the message and the issue, until I reach the same speed of around 55 then the same thing happens again. The message does not appear if I am stationary and rev the engine, certainly seems to be affected by the speed not the revs. Code reader is showing a fault code of P00db- mass air flow fault so I replaced the MAF sensor but sadly the problem persists. Cant just keep throwing money at it so was hoping somebody here may have some insight. Every garage I have contacted are fully booked for the next week atleast.

Any advice/knowledge that anybody may have would be most appreciate.

Thanks in advance