r/ncmiata

Picked up a new Miat. I am unfortunately in an emissions county in Texas. The car has the Roadster Sport Header and I am popping a P0421. Anyone have a solution from experience that doesn’t involve spending $1000?

Ticking/knocking sound, really only noticeable at idle, but its pretty substantial. When above 2k rpm its really not loud enough to hear, I've heard mixed things about the ticking sound with these cars, some say that its just the nature of the engine, but id like to see what you all think.