The test with the foam filters is over, they are worse than the K&N.
Image 1 shows the measured value block 032 at the time of September 2020 and there is a small amount of carbon deposited on the inlet valves.
image 2 shows the lambda learning value at which the foam filter 1100 KM were operated. Carbon was eliminated in winter 2020/21
Image 3 shows the lambda learning value after two days of operation with the K&N filters.
1: Partial +5,1% / +4,7%

2: -1,2% / -3,5%

3: +5,5% / +5,5%

The foam filters let through less air and thus the engine needs less fuel and thus less engine power.
Tom