These are two runs back to back of BMC filters versus stock filters. The bike was equipped with Moriwaki High mount slip-ons & a PCIIIr map optimized with the stock filters & the engine temp was regulated at the same level for both runs. While there are some very small gains in the mid range there is a huge loss of power on the topend & the kicker is the A/F went rich not lean with the BMC's. My professional guess is that the BMC's flowed so much air that they caused turbulence in the airbox/intake's effectively lowering the amount of quality air through the throttle bodies.

If you are an optimist & believe that you can get more power out of the BMC's by creating your own mapping then I invite you to try & please let me know how you fare, but the effort involved in installing those filters (with enlarging the pre-drilled holes & finding your own bolts & washers that should be included in the $125 cost) & then having to make major concessions in mapping to get it to flow right seems to outweigh their value as "reusable"

I've already gotten several e-mails about why we didn't make a map specifically for the BMC filters & I am going to answer that question right now. If the BMC filters are making the fuel curve go rich then you would have to lean out the mapping for the lower amount of air the BMC's are letting into the cylinders (regardless of the reason why) & by doing that you are putting less fuel into the motor (less fuel equals less power)

Even though your air to fuel ratio can be maintained at 12.6:1 ( or any other ratio you want) you are still getting less overall volume of air/fuel into the motor.