i can give you a written guarantee that you will gain a minimum of 4wkw with a BMC panel filter! only reason i say that ive seen gains up to 7kw on E36 M3 3.2's from filter alone!
Best is buy the filter go to a dyno! do a run with your stock filter, then do a run with the BMC filter.. if you dont gain anything ill take the filter of your hand for what you paid for it!
Dinan works on single throttle U.S M3's we have six individual throttles asking allot of air!