Symptoms
Loss of power, erratic idle (more so when cold) boost spikes (loss of total power during overtake), excessive smoke under hard accelration etc.
If you contact Nissan and say your having these symtopms with your car, they will probably say you need a new diesel pump but that’s not really true or not always the case.

What you may need is a new suction control valve, AKA fuel pressure regulator in the diesel pump.
Save yourself a pile of cash by doing the following. This how to is based on the Almera (N16 phase 2) 2.2DCI other Nissan’s will have the same valve or similar but maybe be slightly difference due to location etc.
1. Go to Nissan and get the SCV valve(part no NA6860AW42B) it’s about £120+vat give or take

2. Disconnect the battery 10mm spanner (yes I know hayes manual states this for everything but it is important) (you need it disconnected for at least 90mins I personally left it off over night)
3. Unplug the sensor

4. Using a 6mm allen key remove the old valve there will be a little diesel come out but not much

5. Refit the new valve with the new seal and bolts (supplied in kit) make sure it goes in square I worked each bolt a bit at a time to pull it in.

6. Then plug it back in and reconnect the battery

7. Not sure if this is really needed but I did it just in case, putting ECU rest and into self learn mode)
Turn ignition on so all dash lights come on.
Wait 3 seconds
PUMP accelerator pedal 5 times within 5 seconds….
with foot now OFF accelerator wait 7 seconds…
After 7 seconds press and hold down accelerator pedal for 10 seconds…
After 10 seconds the Engine Management Light will start to flash, at this point remove foot from accelerator.
the Nav is now in diag mode, so let the EML flash for a bit. The press and hold the accelerator pedal down for more than 10 seconds. This will then reset ECU and fuel pump etc and put them into learning mode.
8. Take car for a spin. After doing this I have notice quite a difference in the car with power, idle and pulling away with no excessive smoke