The extender pipe "sleeper" correctly refereed to is commonly known as a "02 SENSOR CEL ELIMINATOR" (or words similar)
This bent pipe essentially removes the 02 Sensor from the path of Exhaust Flow & houses the 02 Sensor in a pocket of Clean Exhaust with the pipe itself. (simple really).



These can be found/purchased from most Performance Exhaust Shops.
Goggle: "02 SENSOR CEL ELIMINATOR" for pics & suppliers.
I know this works, because it has for everyone that used one
