The ///M engine can benefit from additional air (mass) intake, however the Dinan design (specifically for the M roadster and M coupe) concerns me. Look at the picture below, the air filter is exposed in the lower air intake (front bumper). While this may provide additional performance I really question the long term effects. The K&N filter is rather durable, but what happens when it gets wet. I’ve heard a report of a check engine light coming on after a car wash. I also look at the amount of rock chips this section of my bumper has picked up and wonder how long a paper filter could last against this kind of impact abuse.
For these reasons I would not recommend the Dinan intake unless it was only for Autocrossing or Track use, even under those circumstances I question if the Dinan design has any advantage over the ECIS or Jim C design.
Update: I have been informed “Dinan is now shipping (for free) filter covers, a la K&N condoms, which are supposed to solve these issues”. I think this shows great customer service and reminds everyone why Dinan is such a popular company to do business with.