Car won't pass a visual with these on the car. Never tripped a check engine light for me though.
Car is mostly track and i swap these in when i go. An altercation with a wall at road atlanta has me searching for a revenue neutral solution to repair. Translation? "Your dumb a$$ is not spending one red cent fixing that car!!!!" I love my wife.
Anyway, the O2 sensors and pipes have very little use. Discoloration on the pipes is from heat. These save a lot of weight over the cats. 18lb savings if i remember correctly. Check fabspeed site for details; pretty high end components. IIRC they were $500 new. With headers and a race muffler, the sound is almost indescribable.