Im thinking 60K when crack was found and replaced. Now almost at 80K. The light has been on and off even after the replacement at 60K. They just kept reseting it and sending me on my way...after "passing" a smoke test. Would come back on within 200 miles.

I only drive it on the weekends since I have company truck. So its been 2.5 years since replacement.

Oddly enough, my wife put regular in the tank and the light went off and stayed off for months.

 

I had to replace my valve cover and gasket at 132k miles on my '08 535i. Turns out it was a crack in the PCV valve interface (according to my independent). Typical symptoms are getting oil burn-off smells in the cabin while driving - most notably after long drives and then stops. Labor costs suck for this valve cover as there are many steps (see all the DIY guides for info).

My technical assessment of the issue as an engineer:
It's disappointing that the valve cover is a composite material as opposed to aluminum as there will be a different in the coefficient of thermal expansion between the block and the composite valve cover. This will prematurely fatigue the gasket (most usual case) or crack the valve cover where there exists stress concentrations. These concentrations over time will fatigue that location and cause cracking. It wouldn't even matter if the composite was filled with a filler to the point of exactly matching the coefficient of thermal expansion of the aluminum block as I can never guarantee isotropic expansions of a molded piece unless the cover was stress relieved (such as annealing the part under controlled temp conditions for 8 hours - maybe thats why the part costs $400+). Even it was annealed, the geometry is unfavorable as there exists right angles where I expect stresses to not be fully mitigated.

If the leak is at the PCV valve screw cap on your valve cover, there are ways to replace just that - of course, you'll want to replace the gasket as well. N54 tech has a good thread on it.

 

Try swapping around your spark plug coils

 

At 80K, plugs and coils should probably be replaced anyway. However, I wouldn't think a bad coil could be related to a lean code?

 

Yeah I thought the same thing. Me and my friend were troubleshooting everywhere to try and fix my lean code and we even tried the coils. But we switched the 1 and 3 coil and my car started running fine again. No problems since.