Hey everyone. Looking to get some insight on what possible issue I could be dealing with. 2006 X3 has been having horrible fuel consumption for about 2 months now. I'd been noticing a loss in power every so often but didn't think too much of it. Last night it started idling rough... an awful shake from motor to tailpipe. Painfully slow acceleration and a really odd noise (kind of sounds like the helicopter effect when windows are down a certain way) only its coming from the engine. I got codes read and it told me it was a misfire in cylinder 5 and there code P0411.. secondary air injection system. I replaced all spark plugs today hoping that would fix my rough idle and bad acceleration but it did not. Any advice?
*note- as far as dash lights go, I have the check engine, abs, brake & 4x4. They've been on since November*