During heavy rain and fog a few nights ago I had fluttering engine symptoms that I've come to associate with sticky turbo vanes - though I'm not certain. I find that when this happens momentarily switching off the ignition resets the car and it usually runs fine.  This time I had to do so half a dozen times in about 6 miles, so the next morning I ran a diagnostic which came up with lots of codes about exceeding the injectors' regulation limits & overboosting the boost pressure limit, glow plugs, air con (that hasn't worked since I bought the car 3 ½ years ago, garage told me it would cost £300+ to fix so I haven't worried about it), P0113, intake air temperature sensor too high, P1592 altitude & boost pressure sensor, & P3101 & P3102 - the intake manifold flap motor. 

I've done a bit of connector cleaning, as well as cleaning up the EGR & the intake flap, and

During heavy rain and fog a few nights ago I had fluttering engine symptoms that I've come to associate with sticky turbo vanes - though I'm not certain. I find that when this happens momentarily switching off the ignition resets the car and it usually runs fine.  This time I had to do so half a dozen times in about 6 miles, so the next morning I ran a diagnostic which came up with lots of codes about exceeding the injectors' regulation limits & overboosting the boost pressure limit, glow plugs, air con (that hasn't worked since I bought the car 3 ½ years ago, garage told me it would cost £300+ to fix so I haven't worried about it), P0113, intake air temperature sensor too high, P1592 altitude & boost pressure sensor, & P3101 & P3102 - the intake manifold flap motor. 

I've done a bit of connector cleaning, as well as cleaning up the EGR & the intake flap, and

During heavy rain and fog a few nights ago I had fluttering engine symptoms that I've come to associate with sticky turbo vanes - though I'm not certain. I find that when this happens momentarily switching off the ignition resets the car and it usually runs fine.  This time I had to do so half a dozen times in about the same number of miles, so the next morning I ran a diagnostic which came up with lots of codes about exceeding the injectors' regulation limits & overboosting the boost pressure limit, glow plugs, air con (that hasn't worked since I bought the car 3 ½ years ago, garage told me it would cost £300+ to fix so I haven't worried about it), P0113, intake air temperature sensor too high, P1592 altitude & boost pressure sensor, & P3101 & P3102 - the intake manifold flap motor. 

I've done a bit of connector cleaning, as well as cleaning up the workings of the EGR & the intake flap, and the car starts and runs fine though the flap motor code won't clear - but now I have an oil pressure warning once I take it over 1500 revs. Needless to say I took it the ½ mile home at a very slow speed. Some of the fault codes have returned -glow plugs, air temperature, altitude & boost sensors - I don't have the right connector for my pressure gauge, but I'll get the sump off next and see what I find... Perhaps it's just crud at the ECU (which I haven't found) or abraded wires?
Both helpful and rude comments welcome. I hope you enjoyed this news.

If the oil pressure switch is physically located anywhere near the intake flap valve, look carefully for wiring damage in the loom, possibly caused by moving stuff around during cleaning operations.

Pressure switch has a single black wire connection.

Good advice thank you Pete, but now I've borrowed my mate's oil pressure gauge, which gives me about 5 bar so with all those other codes throwing up too I'm looking for the ECU... I think it's under the windscreen wipers.

Oil pressure switch connects to instrument cluster, not ECU.

ECUs are generally massively more reliable than wiring looms.

 

Ah... Into the spaghetti then... Cheers!

The loom looks good, but there are a few earth ring connections to bolts just behind the left headlamp which were in a terrible condition. A bit of wire wool & a broken sharp screwdriver blade, some Vaseline, all connected back up again & all faults are cleared, no alarms.

I'm so happy I'll treat the rust on the doors soon.

Good work and useful feedback, well done. 🙂

Great while that lasted. All codes returned after about a mile, car was just about running. No oil pressure problem though, on the bright side. 

Eventually I found that the trigger that releases the large electrical connector, also behind the left headlamp, was broken & wasn't really holding the halves together. Cable tied together, all faults cleared, car runs really well again. Thanks all.