p38 n reg high fuel consumption

hello every one im having problems with my p38 range rover 4ltr on a gems system is doing around 7 mpg i have done a few things to it to try and sort but i am now stuck for where to go with it
list things changed to also fix miss fire to lamda sensors,ecu temp sensor,and also 2 diff maf sensors cheap 1 and second had original 1
i am a ford mechanic of 15 years but have now been out of the petrol world for some time and mainly do diesels i have a code reader with live data and been checking lamda sensor readings and getting 0.15 to 0.25 swithching when reved but not sure if this is enough of a switch or a lo reading does any one know if this is ok or have the correct readings 2/i have been looking at the fuel trims shrtft is reading 24.2% at idle and swithches when reved back to 0 % but returns back quick if u let off the throttle the lontft is stuck at -100 and does not move at all does these mean it over fueling?3/ does any 1 know the sort of maf readings ishould be getting on idle and under load and also if it a 12 volt feed of 5 volt feed to the sensor so i can check voltage i intend to check for air leeks at the weekend around inlet manifold is there a common fault with that of any other idears ? would really apriciate if some 1 could help many thanks in advance

Engine ECU temp sensor failure? If the ECU thinks the engine temp is low, will fuel accordingly. What colour are the spark plugs? If black & sooty then definitely over fuelling. This sensor is different than the one supplying the temp gauge.

hello i have changed the ecu temp sensor on the front of the inlet not the single wire one next to it for the dash temp disconected that one and made sure

Check the wiring loom over the front of the engine (where the v is). The alternator feed can short with the injectors and effective run some of the injectors permanently. You might get an "alternator fault" warning if this happens on a regular basis.