Well, Napa finally has an after-market air filter and cabin air filter out now for my '03 4-cylinder.
Up until now, nobody locally had aftermarkets and the Toyota dealer charged $22 for the air filter one last time I looked vs. $12 at Napa and $28 for the cabin vs. $22 at Napa.
Well, I'm exaggerating a bit, but I had to stand on my head, recite Japanese and curse colorfully before I could get the air filter box cover to snap back into place. Seems that Napa made the rubber edge gasket fairly thick on the air filter, which made it hellish to get the filter into place. Hey, for the $10 savings, I managed, but was not happy.
The Origninal Toyota filter is fiber medium all around, no rubber at all and on the edges where the cover snaps down is about 75 percent thinner than the after-market replacement.
The cabin air filter was a little fussier than the Toyota also, but did snap in without TOO much trouble.