I am not fond of these things, I think they belong on a Golf or Honda, but then that's just what I think, and it's your car.
This has always been a very hot topic and these things have both advantages and disadvantages.
The factory replacement elements for the stock airbox are "nice" because you can clean them and do actually flow a bit more air but they are quite pricey and allow more dirt through regardless of manufacturers claims.
The cone filters might look cool, but other than that all you are getting is an intake noise upgrade and nothing else, probably a power downgrade and I'l say it again, go look up Helmholtz resonators, BMW intake systems are full of these and in a specific application will out perfom a cone filter every single time.
Something most people don't realise is ALL BMW stock air intakes are CAI already, they ALL have ducting that take in cold outside air from either behind the headlamp grill or inside the bumper cavity. If yours is taking air in from the engine compartment then somebody has probably lost or never replaced a few pipes the car was shipped with.
lastly modern cars use MAF (Mass Airflow sensors) for the intake air measurement. These usually consist of either a Platinum wire or Platinum film that is electrically heated and the cooling effect of the intake air is measured. This thing needs to be kept super clean to work and any filter that takes an oil on it tends to depost this oil on the MAf sensor and wrecks it. The Golfs/Opels etc get away with this because they use MAP (Mas Air pressure) sensors that cannot be damaged by oil.
