hi to everyone Im a newbie from Walton on Naze Essex, I wonder if anyone has ideas on a performance problem ive got with my 2.5 diesel automatic, its the BMW engine and i believe is meant to perform well but mine is as exciting to drive as a milk float with a missfire

.... the car will initially pull away well and then seem to die as if the turbo has cut out, a rolling road test revealed 62bhp at the wheels,A tech test at Vauxhall discovered no problems at all, the turbo can be heared whistling up if i keep my foot hard on the floor it seems to run out of diesel, she is averaging 40mpg,she starts on the button everytime and generally drives lovely, i can reach a top speed of 100mph in about 60secs, and a kickdown does very little apart from make the revs a bit higher. any suggestions will be greatfully received, thanks Terry
P.S Ive changed the diesel filter and run a good quality injector cleaner through.