DIY Disclaimer: I hold no responsibility should anything goes wrong when you decided to follow my guide. It’s strictly meant as a reference for knowledge sharing purposes.
2007 BMW E90 N46B20
Mileage: 92k km
Been losing engine oil badly due to leaks and valve cover gaskets seems to be one of the culprit.
Last change was during BSRI period in 2010 ( about 2 years ago) and I figure it may be time to change it. Surprisingly, the gasket price has come down drastically to now the original gasket only RM180.
Item 2 below is the gasket, it comes in 2 pieces as shown in the following illustration. My leaking culprit seems like the inner piece.
Item 3 & 4 below is the spark plug tube O-rings, only 2 tubes are accessible without removing the Valvetronic motor.
My reference material for the DIY:
http://www.youtube.com/watch?v=GmZ09lz97kE
Just follow the above YouTube guide and below are some shots I managed to get my camera man to shoot:
1. Microfilter, its tray and other covers taken out:
2. Need to unplug the Vanos sensor sockets and flip the harness over the engine cover to clear the path for rocker cover remover, also remove the 2 wires from the positive jump start terminal, as advice by the YouTube above. Don’t have any bungee cord with me, but have plenty of raffia strings.. 
and that’s how I secure the hardness away from obstructing the valve cover.
3. Most of the 16 pieces of size 10mm screws are easily accessible except for the one at the upper left corner in the photo, near the firewall, a bit of back breaking persevere bend-over will get the screws out.. 
When installing the cover, please use the common cylinder head tightening technique of begin tightening from the centre.
4. A blow up of the above photo seems showing the oil cap gasket is the culprit.. 
No the valve cover gasket!!
5) Oh.. well..
6) Severe wetness around the Valvetronic motor..
7) Close up on the wetness..
8) Viola! Forgot to pull out the No.1 ignition coil.. 
9) 91k km almost 6 years old engine exposed!
10) Sludge-free Ignition coil 2 and 3 not removed. Spark plug tube for spark plug No.4 had to be unplugged from valve cover because the Valvetronic motor is the way when lifting/sliding the valve cover out. Meanwhile you will notice there no gasket sealant applied before. Last job was done by Ingress Auto (Authorised Service Centre).
The following are the spots where I applied gasket maker sealant.
11) The bigger picture.. Many dried leaves near the rubber seals around the microfilter, had to vacuum them out to prevent them from entering my engine after the valve cover been removed.
Extras:
I took the opportunity to check the oil separator which is connected to this breather hose. The oil separator is actually a spiral inner cavity plastic device to cool down engine crank case fume / breath and catch the oil to divert it back to the oil sump. It has a recommended lifespan of about 100k km and start to clog up resulting in breath difficulty to the engine. I connect a short section of garden hose to blow into it. I find no difficulty blowing into it means the oil separator not clogged. So I’m in no hurry to replace my oil separator..
And this are my ignition coils.. for my future replacement reference.. so looks like it’s a Bosch 0221 504 100
Another trick I want to show is the oil cap fastener. There’s only 2 metal piece securing the cap to the valve cover and depressing against the rubber gasket within the cap to prevent oil from seeping out. Over time the rubber gasket harden and need replacement, the gasket is not sold separately and a new cap cost RM60. To prolong the life of the cap, I press the 2 metal fastener against the gasket as per the direction shown below. This will result in a tighter seal to prevent oil from seeping out.
Also I saw the the oil cap gasket like leaking..
So I pry out the oil cap gasket to check its condition.. notice the pressed marks below, the rubber gasket still soft, so I flip is around and reinstall it. Now monitoring my oil level, so far so good. 
Thank you for reading and please provide feedback or query if any.. 
