Can I take off the rubber hose that connects ISC or ISA to the intake pipe and then put a filter on the ISC or ISA?

let me know.

 

This has been discussed before, but I will answer your question.
no you cannot. The reason they can do that in Korea is because they are MAP based, not MAF based like the US spec tibs. If you swap to MAP based, then you could do that.

 

^^^ true.

If you have MAF, ESU will not detect air that goes to engine at idle.