how can i fix my zafira?

my 2.0 dti was difficult to start in mornigs and gave out smoke but when car was warmed up no smoke and running fine so put it in to my local garage for a service new oil iol flush filters etc he also cleaned out the egr valve and showed me the carbon that came out of it about a full spray can lid full of carbon he also told me that i had leking iol seals at the turbo which i did but on taking the car up the road i only had about half power so i went back to see him and he said he thinks most of my probl;ems are from my turbo so i sheeled out £340.00p for a new turbo got it fitted and still only got half power could it be the erg valve is just knackered as the turbo is not kicking in at all its got me at my wits end any help or suggestions i would be most gratefull