*HELP* Valve cover repair gone wrong?

[Sporah]

Hello all!
Quite new to this site, looking for help
I have a 2010 535i xdrive N54 which I love!
Last week I found out that my valve cover was cracked, I also found out how expensive it is to have done. I noticed oil build up in the spark plug holes and in casting holes as well as seeing it burn off when it reached the downpipes.
I replaced my valve cover unit yesterday, and now I'm having some difficulties.
Before doing the job I disconnected the battery. I cleaned all of the mating surfaces and made sure to follow the DIY step by step. after the new VC was installed, we turned it over and it there was an Immediate engine malfunction and it was thrown into reduced power mode.
I scanned the OBDII and got the following codes :

P0174 System too Lean (bank 2)
P0300 Random Misfire Detected
P054B Cold Start "b" Camshaft Position Timing Over-Retarded Bank 1
Missfire in CYL 1,4,5,6,

Could this maybe be VANOS? Any input appreciated.
Thanks for your time!
-Aspen