Turbo Problem 1.9SE 2002

[Oneillms]

Hi folks i have a Passat 100bhp 1.9 tdi 2002 and past few weeks i have be driving around 60mph. but when i put the foot down a little around 3.5 thousand revs the turbo seems to shut down. and when i turn the car off and start again the turbo works until i put the foot down again. any ideas whats wrong. Plus i did buy my fuel out of asda petrol station. but not anymore. mileage approx 91k

Thanks for reading
Marty