I'm trying to figure out where the air filter goes.

 

What type and year is your MINI?

 

First, remove the suspension...

But seriously, if you have a 02-06 S model, on the right side of the engine (looking from the front) you'll see a big black box (with an 'oil recommendation' sticker on it), with two torx screws on either side of a 'corrugated' plastic hose. After loosening the screws, remove the positive terminal from its clip, then lift up and push forward and the back will release from tabs on the lower box. It takes a bit of effort to 'convince' the top to come out. The filter is under the top. It's yellow, and is likely a nasty brown/black on the bottom.

 

Would help if we knew year and model of you MINI.

 

cabin air filter or engine air filter?