Post-cat fuel trim might be fixed by changing the post-cat O2 sensor. This code is for the front three cylinders. Perhaps someone else can step up with a more definitive answer.
The VANOS has no affect on fuel trim. The VANOS seals must be replaced to restore original performance. This must be the maintenance to which you refer. If the seals are replaced with Beisan seals, they won't need replacement for a long time, if ever.
Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.
Last edited by edjack; 11-19-2012 at 03:39 PM.