Firewall gulley cleanout
 

So on my 2013 X5 3.5d I go to replace the cabin filters when I notice a bunch of collected leaves and decaying organic matter (will turn to mold) under under the filter holder, I notice that I can take out the plastic air channel easily but there's a fuse box or power distribution box under it. Question, how do I take it out so that I can get the gunk out under it ?

Also on driver's side of the firewall, I removed the plastic cover over the brake fluid reservoir and notice more gunk there as well. Seems that there is a drain that is getting clogged easily. Any times on cleaning out these gullies ?

Is there a passage between the left and right side firewall gullies ?

Each side has it's own drain out the bottom.

I cleaned mine out with a shop vac. Then I used an air hose to clear the drain tube at the bottom. If I remember correctly, you can get to the drains from the bottom, but it requires removing the wheel wells.