I climbed under my hood last weekend to change my broken car horn and noticed how dirty my filters were on my cold-air intake. The picture doesn't do justice to how dirty they were as at the time, I took them off, shook them out and got out as much crud as I could. On one side, the airflow side, I couldn't even see the pleats! The new filters came in today so I replaced the old ones. I could have sworn I cleaned my filters not too long ago but I was clearly mistaken. My blackstone tests came back OK so while dirty, the air filters were still doing their job. After the change, the car felt much better. One note is that the dirty filters were redish while the new ones are blue, I guess SLP changed their filter supplier. EDIT: Do people still use 56k or is it just a courtesy warning?