Diesel, poor performance, £3700 to fix!

[Roverron]

Don't forget that injectors suffer from needle valve failure as well as leakback.
So just because you can't see any leakback, don't assume the injectors are sound.

If the valve fails, the injector leaks fuel into the cylinder.
This makes starting difficult if not impossible (at least without Easy Start) because the pressure cannot build up high enough to start the engine.

It also can cause the engine to cut out under full throttle around 3000rpm because the pressure does not reach the expected level so the ecu stops the engine to protect the pump against possible fuel starvation.

So a faulty valve can cause:
bad starting
poor performance across the rev range ( as if the maf is faulty)
cutting out at 3000rpm

Leakback can cause:
bad starting
rough idle and uneven running & vibration (often around 1800rpm it seems)
but doesn't usually cause the engine to cut out.

I've yet to be convinced that the HP regulator, fuel rail sensor and HP pump are common causes, though the regulator is the most common of these three.
One Bosch agent sold 3 regulators in 12months and no HP pumps.
A new regulator is about £150 but the starter has to come off to change it.

Ron