yeah, and unlike the oil filter one I'll be able to quantifiably test flow rates as well as actual collected contaminants and passed contaminants as well, so it'll be interesting, its just super expensive. with oil filters only costing a few bucks to maybe a little over $10 a piece, air filters start at around $20 and go to well over $100. luckily I've had a few people donate some filters and money to help get the filters, which helps, but its still slow going. I've got my testing rig all designed and am building it, and I've got a few filters too, but I need to get some more before the testing actually begins on it...
I'm also planning on a spark plug test in the future as well...maybe a thermostat one too....but those are just ideas right now, haven't really designed anything specific for them yet.