Engine Malfunction light, cleared but power has dropped 1.6L TDCI

A few weeks back I had what felt like a misfire, but on a diesel. This was in congested traffic in town.
Immediately the Engine Malfunction warning came on and the car went into limp. Shutting the car off cleared the malfunction warning, but the car still stayed in limp.
When I got home I was able to put the code reader on and the following codes came up:
P2290 Low fuel pressure
P02FA Diesel Intake Air Flow Position Sensor (Confused by this one)
P0234 Overboost
Not had the car long so not sure if any of these were already on the module, but had done 500 miles before the issue came up. Mainly motorway miles.
The code reader was able to clear the code and the issue so far hasn't returned, but the car is definitely down on Torque.
Based on the codes I changed the Fuel filter asap which I'm sure was needed but no increase in torque. I put BP ultimate in itt he other day and that's made things better, but not a good as before the issue.
Any ideas where to look?
I'm thinking injectors? and as such how easy are they to clean?