Uni filters do a pretty good job of dust removal because there’s no single path for air to take through the filter. So any dust particles end up flung against the tacky oiled surface.
They are perfect for pre-filters for an otherwise underperforming filter (i.e. K&N).
UNI actually tests their filters in high dust environments like Baja. While my dislike of oiled gauze filters is well-documented here, oiled foam is NOT the same- it has much better filtration.
The downside to oiled foam is that it needs frequent service to maintain its performance. If left in place too long, they get really restrictive really fast.
In a pinch, chainsaw bar and chain oil makes excellent foam filter oil.