Tried looking it up in the manual, found only a small blurb that states "Microfilter/Charcoal Filter"....so uh, are they the same thing?

If so, I guess I'll put it back in when the car goes in for Microfilter replacement :wink:

No, they are not the same. The microfilter replacement that shows up in iDrive is for the passenger compartment ventilation system. It is a carbon coated filter for dust & odors.

Thanks, where in the engine bay is it located?

Two of them, one on the right and one on the left.

Just had mine replaced. Although the iDrive say 20,000 km to go but when I took it out it was full of dust and dirt.
After replacing it, I can feel more air flowing through the air ducts.

You also might be thinking of the charcoal filter, which is installed in E60s for sale in the US. It's in the incoming air stream to the engine, not to filter the incoming air, but the keep fumes from leaving the car (presumably unburned hydrocarbons). Some people remove this filter and believe there's a performance increase as a result. See this thread:
http://forums.e60.net/index.php?showtopic=21796

Yes that's the filter for air going into the engine which I don't have.

If he's referring to the microfilter on the iDrive screen, it is the filter for air going into the cabin.

So, how do I get in there. Are there clamps etc?

Nooooo :P :P