There are two holes on the end of the f-max downpipe for the o2 sensor. I believe I'm using the one closest to the front of the car, leaving the one closest to the cat open. Does anyone know what size bolt I need to get to fill that hole? I believe it is 3/4" fine thread, but I have been unable to locate one of that size anywhere.

 

i would call fmax and ask them to send you the bolt to plug the hole. its suppose to come with the kit.

 

It would be weeks before I ever got anything from f-max, so I'd rather take care of this myself.