Review on Spectre Engine Air Filter SPE-HPR10464: High Performance Premium Washable Replacement Filter for 2006-2014 BMW 128i, 328i, 328i xDrive, 325i, 330i, 130i, 328xi, 325Xi, 330Xi by Dustin Berry

Overall this is a great air filter. It fits perfectly in my airbox, just like a standard filter. I can't say there was a noticeable increase in throttle response since I have an atmospheric engine. However, there was an increase in mpg. With the standard paper filter, I averaged 22.8mpg. With this ghost filter I am now averaging 23.2mpg. That's an increase of 0.4mpg. Quick Count: I ride about 55 miles a day. With a 0.4mpg increase, I drive an additional 2.2 miles each day. Doesn't sound like much, but it adds up. That's 11 additional miles per week or 572 miles per year. Divide that by 23.2 and multiply by the current price of premium gasoline (about $3) and you get $76. In principle, this filter pays for itself in one year.