Ok...so I replaced the sensor...mine also is the brass one on the right. RealOEM either has the wrong part listed or something, maybe updated version because so many go bad? Who knows. So I put the $70 brass one back in and I'll return the $130 version. So I saw a post where a guy said it took ten minutes to do. It took me about 15 minutes....I had to clean my airbox and filter...that added the 5 minutes. And to be honest, if you had an angled wrench you wouldn't even need to removed the airbox and it would take about 2 minutes. Hardest part was putting the airbox cover back on trying to snap it in place. That's a monster air filter in there though. I'm going to search for an upgrade I think for higher flow since mine is a bit dirty...I'm sure it's never been replaced either. I did mine on an empty tank of gas. I got an initial hiss and nothing came out when I unscrewed the sensor. Super easy job but I've rebuilt a M3 engine (inline 6 version) just by looking at the pictures. I'm an engineer by trade so this is all easy stuff. Even a novice can do this though.
So moral of the story....if you have a 08 M3 IT IS THE BRASS SENSOR! I'm glad I ordered both to clear that up because I wasn't the only one confused here I saw. My car seems to idle better, more consistent anyways and it seems to have a bit more pep. It's 80 degrees outside, I'll wait for when it's cold to know for sure. As for codes...well I cleared the codes a week ago and they haven't returned before I changed the sensor. So I'll monitor the car for the next few weeks and see if any come back. I should maybe invest in an extended warranty since I'm at 91k miles. But other than this cheap sensor I haven't had any other problems and I relate the sensor issue to a tank of bad gas. One thing I noticed also, the BMW P/N on the sensor I removed is not the same as the one I put in it yet both sensors look identical
Who knows...don't care. Until the next problem arises.