Any help on this matter please?

I have a 3ltr V6 diesel 55 plate, it has developed a nastie little fault that is stumping all of us, when you drive on a flat road it's fine, as soon as you want to go up hill or overtake the car stutters and miss fuels, full power no power, lift off and it will run ok, on cruise it runs ok, until you load it up then judder. The fault code that came up was pressure sen' for the fuel rail, garage recons that fuel pump might be the problem.???