As some of you know, I'm very skeptical when it comes to power increase claims for most mods, including exhausts and so-called "cold air intakes." While you might get some power increase (and usually at the expense of low end torque loss with exhausts), my view has always been that what small % power increase there might (or might not ) be, isn't perceptible by most, and certainly isn't worth the $ spent. If you want a louder exhaust, great--spend the money to get more sound. An intake system might, likewise, increase intake and exhaust note--terrific. But I've never subscribed to the theory that the money spent on these mods would yield significant power increases that a normal human being could detect, and certainly not relative to their cost.

If you haven't noticed, the air intake on the US 545i (perhaps on other E60 cars) contains an additional filter element (a US emissions requirement) that is a hydrocarbon trap, which is not found on ROW cars. More info here:
http://www.engelhard.com/Lang1/xDocI...up1/SubSiteID0

There has been a bit of discussion regarding this on another board, since this additional filter element is not present on ROW cars. I decided to remove this filter, based on discussion on m5board, and the post below, showing a very easy removal DIY (the pix are for an M5, but I removed the filter on my 545i using them):
http://www.m5board.com/vbulletin/showthread.php?t=66688

While I had the intake cover removed, I cleaned the lower intake area, which had a surprising amount of junk in it (after only a year), and I took the opportunity to to clean the orange air filter by tapping it on the ground with the bottom side down, which released a surprising amount of debris.

Then I took the car out for a drive. Did I feel an increase in "seat of the pants" power, an increase in throttle response, or notice an increased intake or exhaust note? Who knows??!! I only drove for 5 minutes, and it might take longer than that for the ECU to adapt to whatever increased air flow might exist. But I do feel comfortable that, since this filter is only required on US cars, I haven't compromised the filtration of the air going into my engine, while at the same time increasing the air flow (by how much--who knows...), which can't be a bad thing--freer breathing equals more power, right?!