O2 Sensor Extender & Spacer
 

Reading that O2 sensor extenders and spacers can be used to run a catless header on brz/frs without throwing a CEL code, in the absence of a tune. Any experience or insights into effectiveness of extenders and spacers on our engines would be appreciated.

have a read of the Basic Bolt on Mods link below

the spacer in the rear 02 sensor bung will often fool the ecu into not tripping cel code p0420 but will do nothing for power.

the spacers dont always work and sometimes the code will still trip but maybe less frequently.

you rearly need a tune or your wasting most of the gain available from catless headers.