So if the EGR is not working at idle (full vacuum), then the mixture goes lean?
Egr definitely should not be working at idle. The test, at idle, is to apply vacuum to the valve, which opens it, letting exhaust into the intake and causing the motor to stumble or die. Mine fails this test.
I do not believe the egr is affecting mixture. It's purpose is to lower combustion temps which will reduce NOx. NOx is caused by the high temps which can be made hotter with a lean condition.
