Is it necessary to replace it? I ask because the oily sponge air filter on my VP 2003 is always squeaky clean. That's designed to be cleaned - officially you're supposed to wash it in clean diesel and then squeeze as much out as possible - but it's always so clean that I've never actually bothered! And as the air is drawn from the engine compartment and then via the cockpit locker, it's hard to see where any dirt would come from. It's not like a car that's drawing in air full of road dirt; the air supply for our engines is pretty clean to start with.
I’ve got one of those on my VP2003. Seems fine.
I was going to ask how these affected induction noise (great when modifying your Cortina/Mini in the 1970s but a bit of a headache nowadays). Then I found this thread discussing the same .. D1-30 Air filter info
When my 2003 filter disintegrated, I made up a new one from a suitable sized "Tupperware" container with suitable holes drilled in it, and washing up sponges - green coarse filter on the outside, fine yellow bit inside. It worked fine
