Service Engine light and Oxygen Sensors

[Riggodeaux]

Update. I continued to get the Peake Table 19 F5, F6 codes [P0491,492 on Autozone's OBDII scanner] and added a table 19 3d code [post-cat O2 sensor] so I stopped by the dealer and had them do the official bmw computer scan. It tied the F5/F6 codes to the secondary air pump check valve and confirmed the one O2 sensor. The dealer's tech, always looking for billing opportunities, noted a leak around the valve cover gasket, too. The price quotes: $685 to replace one post-cat O2 sensor, $566 to replace the secondary air valve w/gasket, and $575 to replace the valve cover gasket. All easy DIY tasks, so I've ordered the parts [for these alone, less than $200, saving $1600+ over dealer rates] and will do the other O2 sensors and now-overdue sparkplugs while I'm under the hood. I don't notice symptoms, but I may do the preventative DISA valve repair [G.A.R. kit] while I'm at it. Any thoughts?