2005 Volvo V50 Engine splutters and has no accelleration

Engine Performance problem
2005 Volvo V50 Two Wheel Drive Manual

hi we have an engine issue which volvo say they cannot fix. the engine get very sluggish and poor accelleration and dark fumes frm exhaust.
we have had the turbo changed the EGR valve has been changed and engone fuly stripped
the particualte filter and just about everything.
we have spent over 5000.00 on attempting to repair it but volvo recommend things which we do and they dont seem to work can you advise if you have heard of this fault and how can we repair it.


thanks

David