one thing to consider ..
be the possibilty of sticking turbo vanes ..
i.e. if the vanes get stuck in the strong-boost position
the turbo can over-boost .. causing the ecu to limit power
( so likely to happen at higher rpm foot-to-the-floor )
so looking at the MAP sensor as well .. comes to mind ..
( maybe it's clogged up with oily manifold gunk )
so 'limp-mode' in your case = sudden loss of power and dash warning light ???
asking as the m47r/td4 lump looses bhp after 4000 rpm ..
and feels like it ..
( standard m47r/td4 power graph pic. attached )
and .. what brand fuel filter did you install ?
i.e. a cheapo one just might give issues under full go-pedal higher rpm demand
( if the fuel pressure is restricted when demanded by the driver
( the ecu will limit power to prevent damage to the h.p. fuel pump )
some hissing by the h.p. fuel pump is 'normal' by all accounts
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suggestion ..
if you want to take advantage your td4's torque/bhp set-up
concentrate on improving the sub 1800 rpm range ..
e.g. fit a straight-thru design exhaust back-box ( a de-cat would also be very helpful )
'delete' the EGR unit ( probably first and foremost )
install a good tuning module or get it remapped ..
modify the air-intake design using alloy tubing and heat-insulation
the pre-air-filter air-intake-route be the critical one ..
for added lower end torque install a 'dgb1' turbo controller
and set it to "L"
the above Minus the tuning-box/remap/turbo-controller .. will give you much better power response
( acceleration ) from 1500 rpm and above ..
adding the turbo controller gives a bit more ooomph thru a chosen rpm range
safely boosting the fuel injection just adds more power thru the useful rpm range
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few useful links ..
rover ron's tuning website :
http://tuning-diesels.com
td4 engine faults :
http://tuning-diesels.com/75Zt/R75faults.htm
about the 'maf' sensor :
http://tuning-diesels.com/75Zt/R75maf.htm
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more or less how the m47r/td4 engine operates :
https://www.landyzone.co.uk/land-rover/td4-m47r-engine-pdf-file.288724/#post-3564507
the 'link' in post 1 .. still appears to be working
be some diffs. ..
no in-tank f.pump on later models
the text doesn't cover the td4's variable-vane turbo
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and the attached graph ( standard tuned m47r/td4 engine )
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