Thanks for taking the time to dyno the drop-in filters.
Your results mirrored my butt dyno when I did the K&N drop-ins recently.
Last year I installed BMC drop-in filters and felt a substantial loss in power everywhere. My thread
here
I decided to switch immediately back to the stock filters and decided to stay with them until last month. I was still curious about drop-ins because I planned on going to an E30 tune, I thought let's give K&N a try since I had a good experience with them on my E92 M3.
After installing the K&N drop-ins last month, it was a nice improvement over stock, the car just felt more responsive, mid-range felt like it picked up a good amount. Glad to see the data to confirm my suspicion.
I initially bought the BMC filters because of recommendations from a few forums members and vendors, hey if it comes stock on a GT3 than it should be good enough for the S55 was my thought.
From my experience, BMC filters do not work well on the F8x, I felt a power loss and sluggish throttle response. K&Ns on my car seems to work amazingly well, even better than the stock filters which I thought was the best setup until recently.