It's required for the older style cats that came from the factory on our trucks... the extra atmospheric air in the stream is what helps the reaction start and continue inside the cat.\The generally-accepted opinion here is to not remove it unless tis bad, as tis supposed to help the cats do their job so it kinda-sorta-maybe helps keep pollution levels down.]
On a truck, when is the air pumped by the pump diverted to just vent in the engine bay? SEFI cars ('86 and up) do this within about 10 minutes of starting the engine, pretty much when the engine is all warmed up - ECM changes the voltage on one of the solenoids, the solenoid changes the vacuum signal to the main diverter valve (the big one right behind the air pump), the valve closes off the exhaust air supply lines and opens up the vent so all the air coming from the pump just blows off through the vent, hence the very specific "shwoosh" sound coming from the engine at high rpms. Do trucks ever do that, or do they blow air through the cats all the time?It's required for the older style cats that came from the factory on our trucks... the extra atmospheric air in the stream is what helps the reaction start and continue inside the cat.
If you remove the air pump, more then likely if your stock cats are still doing their jobs fine, you'll end up damaging them.