The pressure regulator control valve has been blocked off for years without any issue. Also, would the bad filter cause it to run so rich? I would think a clogged filter would only make it run lean.
First time poster, fairly recent lurker.
I have a 2002 protege5 with problems that I can't figure out. The car ran fine for years and all of a sudden I started getting a bogging/hesitation under acceleration. The afr gauge is all over the place; sometimes idling at 16.x and sometimes idling...