Originally Posted by ripp222

I think TwinTurboGTR is referring to the Secondary Air System. See attachment. Stuck open Non-return valves could allow exhaust gas to get sent to your secondary air pump, but I wouldn't expect this to cause rough idle problems.

I would spend the $35 and review all the SIBs for Group 11 (Engine) and Group 12 (Engine Electrical) on bmwtechinfo.com