Just for reference I'm reposting this thread so it might help others with the same problems.
My car = 1.9 cdti Sri 150hp 2005.
It all started when I bought the car before Xmas, having never had a Vectra or a diesel engine.
Car was a bargain no issues 59k miles on the clock, drove it home to Scotland and it was perfect. Got it serviced at local garage... Next day the spanner light came on and went into limp home mode. Garage said mass airflow metre, bought, fitted, took it for a spin and spanner light again!
This time they said it was possibly boost sensor. By this time they had extorted to much money from me so I found this site and decided to try my hand at some diy.
Bought and fitted new boost sensor, could have cleaned and replaced but wanted to make sure it was sorted.. Anyway never fixed the problem, after reading about comon problems on the forum i fitted new boost pipes to see if that helped, mine were perished with couple small holes, did improve low end but never fixed the fault.
so next was egr, same again could have cleaned but bought one of eBay, fitted in 30mins following the guide on forum, this fixed the fault and I thought all was well! Then while messing around with boost pipes I broke the plastic connection on the vacuum unit at the front right of the bonnet next to the radiator! I thought what an idiot, now have to buy a part I don't even need!
I ordered a new one and fitted today (took 5 mins). When I drove the car to the parcel office to get the part, the car felt ok, but after I fitted the new vacuum... I took it out, driving the same way and the car started wheel spinning taking off at junctions! Boosting from under 1500rpm smooth up to 5000! Feels like a different car now! I'm so glad I broke it Or I wouldn't of found out it was that causing the performance issues.
Maybe this will help someone out there with the same problems, and thanks to this forum and the guides, I saved a bucket load of money that would have lined the stealers pockets! Result!!!