I think this is air flow related. Opposite of p0104. I've generated this code when I ran my car with map sensor outside of the manifold (i wanted to see if it could read atmospheric pressure correctly). This suggests your egr is not closing. P0104 stuck shut.
P1238 stuck open.
I recommend blanking the egr off with a plate on the manifold side. This is very cheap and easy to do and will help your diagnosis. In my opinion it is also of benefit for your engine and betters the cars performance.
Other cheap investigations to eliminate possible causes are:
Remove and clean the map. I bet it looks like a lump of coal and could be giving false pressures and temperatures.
Check turbo hoses for splits.
Check all the vacuum hoses that control the turbo.
There is a plunger on the turbo controller thing which I think changes the pitch of the turbo vanes. It is controlled by vacuum. Check it moves when the engine is started or your vanes could be stuck and not providing sufficient boost at low revs.
Lastly try disconnecting the maf. I've read that if its broken then the car will run better without.
Good luck. Keep us posted if you make progress and be wary of garages just wanting to replace everything under the bonnet!
Last edited by dgmayhead; 17-06-15 at 18:31.