BMW 525 TDS Power Loss

Hello good, I have a 525 TDS of the year 97 E39. For some time the car fails. At the beginning the loss of power was sporadic but it has become all the time. The car does not turn on any electronic failure light or anything similar, the turbo is heard whistling when the car is standing, I have cleaned the flow and changed the filters nothing remains the same, once it works well but suddenly fails again. I hope I have explained well. Greetings and thanks.