I would be at a loss with the original post. From the reply, I agree you are probably talking about the secondary air blower. It does not blow into the EGR though. The EGR takes exhaust and allows it into the intake. The secondary air pump blows air into the exhaust near the valves. Two entirely separate systems dealing with different emmissions issues.

Secondary air is only used during warm-up to burn excess hydrocarbons in the richer cold running mixture. It also works before closed loop as excess air in the system would affect the mixture if the O2 sensor was working. Its main purpose is cleaning the exhaust and warming the O2 and cat.

The EGR on the other hand is used especially when hot to lower the burning temp by introducing an inert gas (all O2 has been previously burned) to displace air containing O2 and cool the flame. This is specifically used to reduce the formation (oxidation) of oxides of nitrogen NOx.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician