Dont have a photo sorry, but I’m thinking you might be referring to the cowl anti ice system.
BB-1266, BL-129 and after have exhaust gas from the left exhaust stack flow through the cowl lip (the shiny silver bit at the air intake entry you can see in the pic posted above by +TSRA) and then exit the via the right stack.
Older aircraft just deflect exhaust gas down into each end of the lip, and this then escapes out the bottom of the lip.
This happens automatically, no need to turn it on or off.