I got make myself a draft for threads like this for everytime they come up.
A DCI setup regardless if it is aFe or BMS etc will produce more gains over stock intake.
However, for the cheaper cost for more gains your turbos will "work harder" to produce boost and they become "less efficient". The reason is because the air in the engine bay is less dense than the "outside" ambient air.
Then other problem is having your BMW engine bay to looking like this
If your not keeping your car or its a lease, then go ahead and fire it up
Sometimes the cheaper alternatives come with an equal exchange ie a compromise depending on what you feel is more important to you.
CAI or Cold Air Intakes are exactly what they are. These are the benefits:
- More Air Flow
- Less Air Restriction
- More Dense Air ie Cooler Air
- Turbo Efficiency
Depending on the CAI it can produce near or even more gains than a DCI
I am running the aFe Stage 2 Elite SI, and it produced significant gains over the stock intake. Both tests where done in almost 10°F difference with the stock intake tested in the lower temps
In the winter weather intake cover can be taken off if your going to be racing and during summer weather cover on. Test above was done with cover on
However there is a general consensus, if you are not running more the 15+ PSI stick with the stock intake, just get a K&N filter replacement and perhaps add air scoops
Top Gear Solutions has the best deals you will find on NEW intakes