I've had my 1985 Toyota Truck since it was a year old. I'm changing the heater core. It was necessary to extract the entire unit that contains the blower...there are several places where a sponge filter material was used...it's totally degraded. Should I leave it or replace it?...If so, with what?...Where can I find it?...Can I just remove it and leave it at that?...maybe it has a function other than filtration? Thanks in advance for any help.

Roger