Aside from reducing exhaust emissions ( NOx ), this valves serves another purpose.
When you re-introduce a small portion of exhaust gas into the intake system, it actually acts as an artificial octane booster.
Meaning, the air/fuel mixture becomes harder to ignite, therefore reduces pinging & also allows more ignition timing advance.
I have seen cases where a non-functioning egr cause pinging ( something you DO NOT want ), and also reduce fuel economy considerably ( because of the lesser timing advance ).
I would replace it.
