I assume you are talking about the pollen filter. We had a big yet inconclusive discussion here recently over whether the ECC had to be re-programmed when the more expensive/restrictive carbon/paper filter is installed. That's because the instructions that come with that particular filter specifically state that the ECC should be re-programmed. But nobody seems to know exactly HOW the ECC should be re-programmed, while a number of other people said it was not necessary in spite of what the instructions said. In my mind the issue was never resolved satisfactorily...