RE the answer below. Coleman furnace 7655-856. Thank U Robert for the answer on the below question, But Can I actually use some other kind, such as pleated, carbon etc. or would it restrict air supply too much? Maybe one that doesn't have a high number rating? There is a vent on the outside door for...

Can I actually use some other kind, such as pleated, carbon etc. or would it restrict air supply too much? Maybe one that doesn't have a high number rating? There is a vent on the outside door for air also. These foam filters look as though they wouldn't hold any dirt.

Coleman model 7655-856. This older coleman furnace doesn't have any filters in the doors. What kind should I use and do they go in both or just one? I was thinking foam?? Both doors have a few slats in them. That is where they do go, correct? The furnace is accessed from a door on the outside of the...