Prevent the P0420 and P0430 check engine codes. Comes with (2) defoulers already assembled with the medium fittings.
These adjustable defoulers can be used to prevent the check engine light when running headers (P0420, P0430) by limiting the amount of exhaust gases the O2 sensors see.
These defoulers are adjustable and have 4 settings, fully open, small, medium and large fittings to change the amount of exhaust gases the O2 sensors see. Easy to install, easy to change around.