I've got two service manuals but neither of them state when the air filters are supposed to be replaced. They only give instructions on cleaning them.
Found several mentions of Uni foam material. Ranges from BF-1 - BF-6. Different colors, thickness, 40-60ppi (I'm guessing the higher number is better filtration?), fine or coarse. Pretty sure I'd go with fine foam & 60ppi but what thickness should I use?If you rebuild your OEM filters using the Uni-foam then you won't ever have to replace them again. When they get dirty, you just clean them and reuse.