I change my engine air filter about once a year (no longer than every two years) with quality filter. When I replaced this week (it's been about 18 months) it looked pretty dusty/dirty, and the cloth-filter attached to the actual engine housing (pictured) seemed very dirty/dust as well...more than I've ever seen it, really.
Q1: is this normal? Q2: is this additional filter layer removable/replaceable?
Q1: is this normal? Q2: is this additional filter layer removable/replaceable?