try injector sleeve it might be drawing air i had same problem with a vectra
There are three bulbs and you'll probably want to change all three.
1. Use a flat screwdriver or old spoon to level the bottom of the fascia. The clip at the front is quite long.
2. The cover is held by two more clips on either side of the multifunction display. So grasp the cover on either side and pull backwards.
3. Display is held by two torx 20 bolts. Be careful not to drop the bolts.
4. Bulbs are held by twist connectors. Twist to remove.
Clean the bulbs before you insert them.
change at least every 25,000 auto transmission oil does not last as long as manual gearbox oil, all to do with friction and heat in an auto box, pays to replace filter as well
Open the hatch, remove the rear interior body panal. Then there are five plastic wing nuts on each tail light housing. remove the wing nuts on the side which needs replacing, which may be obscurred by the other interior panals, and carefully remove the tail light fixture. to remove the bulb, twist the bulbs base left or right, and pull. The bulbs I.D.# should be on the bulb. Hope this helps.