Haven’t had truck long but whilst driving up through the gears all is fine until you hit 40 mph then it just seems to slow up and feels like engine is labouring get to 45/46 and things start to pick up again, this is my first L200 after swapping from another well known 4x4 brand, any suggestions greatly received.

Hi and welcome to the forum.
2006 was swap over year for L200s, from the Classic to B40 New shape trucks, can you advise which shape yours is?
Also do you know when the fuel filter was last changed?

Hi and thanks for the add, truck is new shape and fuel filter was changed in December 17

Check the Turbo boost pipe isn't blocked inside the Alloy tube where it meets the engine (you may need a small drill bit to poke inside)
Also check the rubber pipe for cracks & splits
Pic below.

Cheers il have a look and see