Right Filter for a Lennox 26-21-1 Furnace?

I was told that the filter I have been using a 3M 1250 Ultra Pure is too restrictive making the blower work harder than it needs too and making the furnace try and grab air from where it shouldn't(creating negative pressure)...is this bunk? I have a foam reusable that I pulled out 7 years that I cleaned off today...should I put that back in?




Thanks



Dude