Audi A4 2.0 TDI Balancer,oil pump chain problems

I purchased my audi with 104,000 miles on the clock with full audi service history scince then a melal pipe on the back of the engine cracked costing 390 euros then the pulley on the aircon pump sheered costing 400 euro then the engine was ratteling when i went to the garage i was told it was the chain that drived the balancers and oil pump inside the engine in my car it is chain driven and it was failing so audi has now changed it to spur driven and the parts are 1800 euro so i opted to buy a secont hand bare engine fitted cost 2500 euro now the car has a fault with the diesel injector that is going to cost 500 euro dont buy audi go toyota thats what i will be doing next. Incedentely i called audi uk about the engine fault and asked if there wasnt a problem with the chain driven oil pump why did you change it the manager at audi uk told me everything needs to be updated just like your mobile phone i was not ammused they did nothing