K&N Cold Air Intake System: High-Flow Air Filter, Increase Performance & Acceleration: Compatible with 2001-2005 BMW: 330Ci, 330i, 330Xi, 57-1001

I bought this mostly for sound, but I was pleasantly surprised to experience a noticeable (if slight) improvement in power and response. Apparently the factory air filter box on a 330Ci actually is somewhat restrictive.Install took all of 20 minutes after putting together the right tools. The instructions are nice but if you've done this sort of thing before or are otherwise mechanically inclined then there's really nothing out of the ordinary with this kit.The coupler is a cheap silicone piece. I was expecting to find a nice multi layer, fiberglass impregnated piece but I guess the one that's included is sufficient enough as it's only an air intake.The induction noise is lovely but on light throttle there's a hissing noise. This is the throttle body's fault; I suspect any brand intake would reveal this sound in this car.Edit 6/11/14: Initially I had glowing reviews but after a few months I started seeing strange driveability issues; inconsistent power delivery, etc. Put the stock intake back in and boom it was suddenly a different car & I haven't thought about putting this intake back in. Looking at the filter, one small patch is much dirtier than the rest, so I think the stock intake snorkel just blasts sand and other airborne particles right at it, & I imagine the 'blast' is also a source of turbulence that may exceed the MAF's ability to calculate properly.I was going to try to fabricate my own air straightener setup but after looking at the price of this thing again I struggle to find the justification in spending any more money on it, even to experiment.

Had it installed for several days now. Definitely better respond throughout mid and high rpm. I have 330 CI six speed so it's even noticeable when flooring and shifting. More noticeable on third gear on the highway for passing. She just keep climbing. As for sound, bit of whistling on certain idle otherwise it sounds good. Not loud, but sounds powerful. Engine bay looks better less clutter. Overall I am happy with it.Update: Almost a month after installed. I get almost two more mpg with harder driving. I could get more mpg if I wanted to, but it's good enough for me.

The media could not be loaded. Quite disappointed. With the parts I received I am not even able to install what I got. I received a heat shield and 2 air filters (one new, and the other extremely worn) Seams like this is the only time these issues has been reported to the seller via a review. Whoever is packaging these boxes seams to not care, I received a verry worn air filter that’s basically junk.On the other hand the heat shield and the other air filter meet my expectations. Sean like great quality.

Definitely a throttle improvement and louder engine at the higher RPM’s, only thing like others have mentioned , the filter keeps falling off , I have to keep retightening it every other day, I installed it myself about a month and a half ago and no issues or codes

I appreciate the seller very good product the best investment you can do got it for my 330Ci for stage 3 tune fits perfectly

This product was very easy to install,in my 2003 BMW 330 CI, probably only took about 30 mins or so. In my opinion the sound that comes from the K & N air intake and air filter is a very nice sound! sounds powerful it has a good pitch I can tell that the throttle is more responsive better than the factory air box. personally the problem that I had with this product is im not sure it is worth the money. From the research I have done it is the cheapest price is on amazon.com for this part number and most other part numbers I have researched. So the reason I am only giving it 3 stars is because since installing this product, is because with aggressive accelerating and then shifting out of gear and into neutral when the rpm drop to an idle the engine shuts off. It could be starved for fuel dropping from high acceleration to idle and maybe I just need to replace my fuel filter. There is a few possibilities that I am considering. to much air to fuel! I do not know exactly. I can not guarantee that the fuel economy will go up for you but I believe that has increased about 3 miles to the gallon on the highway which puts me to about 33 mpg at 75 miles an hour. Although my fuel economy in the city probably is the same as before which is about 22- 25 mpg. That is probably just the way I drive in the city though. So if i get the chance to update after replacing fuel filter I will.

I mean it's K&N, you get what you pay for, super solid design and construction, this was the first mechanical mod I ever did on a car and it took me about 45 minutes to install to completion, instructions provided were helpful and I love the slight cold air whistle. The slight power gain helps too...

I’ve always like the sound of a K&N on a car but wasn’t expecting to get better gas mileage.