A4 TDI (AFN) problem

[Scaro]

Hi

I have a problem with my A4 1.9tdi(AFN) -97 that you people maybee could help me with.
Sometimes when i drived my car it felt like the turbo doesnt worked i had to change gear so it revd
 a bit more then it worked i drove it like that for a couple of month (it doesnt happend often)
Then a couple of month ago i was driving the car and it just stopped and i couldnt start it again i checked all i could by my self
but i had to tow it to a repairman. They looked a it and found out that my inj.pump was broken
(the steel bit between the hydraulichouse and the rest of the pump was broken into 2 pieces).
I bought a another inj.pump and they installed it to the car and it worked well for maybee like 8000km.
Then the same thing happened again the car just stopped and it would not start so i suppose the same thing happened
again and this time i can fix it by my self(I know what it is this time) but now to my question why is this happening?
Is there anything with the fuel or what can make it do like that?
I dont want to change inj.pump every 2 month

If you need more info i will try to write it.

Hope you understand what i write i am from Sweden:)

Best regards Oskar