When I required my s60 it had one of these green aftermarket k and n type air filters, I've been reading a few other forums and it seems remapped cars need these, I put a stock filter in which I prefer car is quieter with it that's for sure, what would the best course of action be stick with my stock or clean the other filter and shove it back in, I don't think it would make a huge difference tbh but some wiser heads on here that might tell me otherwise. I've also heard these performance filters also let more dirt in any truth in that