My xB came with a dealer-installed AEM cold air intake. It's obnoxious and noisy, and puts the air filter in the wheelwell.
However, AEM intakes have a bypass valve (in case of water ingestion), so I took it apart at the bypass, and just stuck the filter there, next to the engine.
Here's what I removed:
Ignore the Texas Chainsaw Massacre poster.
...and the racist-caricature lamp.
...and the ashtray inside a bag full of baking soda (it stinks).
Sorry the pictures are kind of big, I already closed the imageshack tabs. Oops.
Hopefully, I get some results in terms of FE. I desperately need to clean the filter, but I'd have to shell out the princely sum of $8 for the detergent. However, this little mod made my car a good bit quieter, so at least there's that.