pug 407 2.2 petrol,depollution system faulty?

hi,can someone help me with this so called "depollution system faulty"paid $9000 for a 2004 model done 102000 kms from a auction and had this problem since i bought it,took it to melbourne city dealership, charged me $143 and told me they guna charge $990 to fix it,i was told that the throttle body needs to be replaced,car drives reli well even though the light flashes,any suggestions my friends ??