2008 5 Series 520d Help!!

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Hi all,
 

I’m a newbie here and desperate for some assistance. I’ve got a 2008 520D with 133K on the clock.

 

I was driving home Sunday after a long drive down the A34 and when I put my foot down there was a terrible lack of power and a siren-like sound from the engine area. It seemed to correct itself and I managed to get home. That evening I went to visit a friend and I got no more than 1 mile down the road and heard a terrible hissing noise and lack of power. 
 

RAC attended and found a rubber hose (pressure pipe from the DPF to the engine) had blown off. RAC said the DPF was blocked as it had reached its end of life and towed me to a garage. 

Initially thought it could be the turbo but the garage confirmed DPF blocked and I needed a new one. They fitted a DPF and did an oil and filter change today. I went to pick the vehicle up this afternoon to find the technicians all crowed round my car (still has a lack of power, although no whistle). Eventually they told me that the turbo was full of soot, due to DPF block and that the car ‘just needed a run’ to free the turbo vein’s.   

I got the car 5 mins down the road and sure enough the same pressure pipe has burst off again!

Has anyone seen anything like this before?! Sorry for the long post. I’m at my whits end and I just want the car fixed!!

Any help/advice would be great. Thank you!