3lt Nissan9

I have a Nissan Patrol 3.0 ltr turbo diesel 2008 ,around 4months ago well driving it started losing power have had it in Nissan for about 3 months and the menc cant seem to find the problem have just picked it up and got it home , it is worse then it was can drive it slow as soon as you go to 2000rpms stalls and you have to turn key off and back on to start the car again , loses all power and like it goes into limp mode( no warning lights or anything come on ????Nissan had it up on host and they could get it to120 mph fine didn't stall at all as soon as they started pulling hand break and putting it under load it dies ?the only code coming up they said is large fuel leak , have been through the whole car replaced all fuel lines and still made no difference ? any help at all would be great at this point .have had itfor 18 months

hi I have a Nissan Patrol 3.0 ltr turbo diesel 2008 ,around 4months ago well driving it started losing power have had it in Nissan for about 3 months and the menc cant seem to find the problem have just picked it up and got it home , it is worse then it was can drive it slow as soon as you go to 2000rpms stalls and you have to turn key off and back on to start the car again ????Nissan had it up on host and they could get it to120 mph fine didn't stall at all as soon as they started pulling hand break and putting it under load it dies ?the only code coming up they said is large fuel leak , have been through the whole car replaced all fuel lines and still made no difference ? any help at all would be great at this point .have had itfor 18 months