Air Filter or not

[[email protected]]

I recently added an air filter from Snyders or Bratons, can't remember.
The air filter is made to fit works well and has a metal element.
I have been told that an air filter of any kind is too restrictive and can make the engine run too rich.
The carburetor (Zenith) is not designed to have the restriction this air filter brings. Even a metal filter.

Is this a true fact?