gasket or insulation under air filter
 

When changing my air filter I encountered a problem putting the cover back
on. There was a gasket or a cover that is located under the plastic case. This piece was all ripped and deteriating. I took it off. I would appreciate it if anyone knows if I need to rush out and get a new one. I don't even know what the part is called. It seems to be working fine without to part. I am not sure what the part was used for? I would think that there was a purpose for this cover?
Thanks.
Eric