A Throttle Controller is the best Bang For Buck thing you can do to your modern Turbo Diesel.

Since the introduction of Common Rail Diesels, vehicle manufacturers also adopted Fly By Wire (FBW) sytems for the accelerator pedal. Most FBW turbo diesel vehicles have an inherent lag from when you press the accelerator pedal till the engine responds. Often referred to as "Turbo Lag", it is more accurately described as "Pedal Lag"

A Throttle Controller is simply an electronic device that plugs into the accelerator pedal and intercepts the signal before it gets to the vehicle's ECU, allowing you to change the throttle sensitivity depending on your driving style.

Sinister Offroad stock Throttle Controllers from Ultimate9 with their EVC (formerly iDrive) and EVCX range, Direction Plus' TR+ range and SAAS-Drive by SAAS.