I have a couple of somewhat unrelated questions about the smog pump and EGR valve on a 93 190E 2.6.

When does the smog pump run? Is it always on or only when the car is in open loop when the car is just started? Also how does it work? Is vacuum on mean the smog pump is pushing air into the exhaust or other way around?

Second, is having a non-working EGR valve bad for the cat and O2 sensor because of all the excess nox particles?