Did the dealer use the proper Vauxhall "Tech 2" Diagnostics?
Vauxhall diesels often wont communicate with generic code readers. I'm assuming it's a proper Vx dealer.
A common fault with these is the Mass Air Flow (MAF) sensor. This can also cause emmision faults as it gives the engine computer wrong info on airflow. A good quality replacement MAF is quite expensive to buy, but a simple DIY fit. Copy and paste link-
http://www.autovaux.co.uk/LoadPortal.aspx?cnum=11&pnum=AS93178243&tabid=5&vnum=137
Dont bother with cheap ones off auction sites, they are cheap for a reason.
You could try borrowing one from a known good car.
I wouldn't spend money on parts until getting the diagnostics done by someone competent.
There are so many systems and sub systems which can cause problems replacing parts at random will bankrupt you.
A half-decent tech 2 operator should be able to scope the MAF and other sensors and actuators using the live-data function, a GOOD operator will be able to spot any anomalies in the various outputs.
gus
November 2009