Synthetic, and it was sealed in the bag too. I was as surprised as anyone, butI didn't think to check for manufacturing dirt inside it beforeinstalling iteither. Had I, I may have blown it out w/some compressed air first.

 

is there alot of maintenence involved with a cold air intake?

 

I would definitely gothe AEMroute with Dryflow filter. It's simple to clean and you don't have to mess with oils. Here's what they say on the AEM website on how to clean it. There's even a video on how to clean it.

"Frequency of cleaning for your DRYFLOW filter will depend on the conditions in which you drive. As a rule, we recommend that you clean your filter a minimum of every 30,000 miles, inspect it during oil changes and regular service intervals, and clean it if it appears to be reaching its dust holding capacity. If you live in particularly arid, dusty climates or venture off road, we recommend cleaning the filter every 3-5,000 miles. Keep in mind that a clean air filter can increase fuel economy as much as 10% compared to a dirty air filter, and service time for the DRYFLOW filter is only approximately one hour, so you can accomplish it in about the time it takes to change your oil."

I will be purchasingthe AEM with dryflow filter next week for my 07 M3. I'm also opting for the water bypass valve just for piece of mind. It's very dry where I live but when it rains heavy it does like to puddle up quite badly. My brother just installed the AEM/dryflow filter on his Accord and he said he notices quite a big difference when passing on the freeways. I'm sold.