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The EGR system takes in a certain volume of exhaust gas and reintroduces it into the intake charge. Since this gas will not combust, it takes up some of the volume in the combustion chamber, less air and fuel charge is allowed in the combustion chamber (helping increase fuel mileage). Also, as the exhaust gas is unburnable a second time, it is much cooler than the ignited intake charge, therefore acting as a cooler, which is why it reduces NOx (more heat, more NOx).

Cars designed with EGR valves will typically fail CA smog without it functioning. Toyota has taken engines that have had EGR valves and done away with them on some other models (1MZ-FE for example has EGR on camry and avalon, but not sienna) Early 4 cyl tacomas have egr, but not the newer ones. Somehow they have done it with computer programming or cam timing or something else they don't disclose.
 

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wow, its been a while since I've looked at TSI test numbers, so used to looking at failed ASM tests since oct 04 when CA started using the dynos. How's your tune up, looking at the high hc at idle shows a lot of unburnt fuel coming out. Does your car idle smooth? Looking at the 2500 numbers, I would say its running rich, the idle numbers looks more like it has a slight misfire. Hard to say without looking at the car, though. Have you checked if the O2 sensor is reading correct?

Its been a while since I've had to diagnos smog failures, so I'm a little rusty at it.

Also EGR, functioning or not would not have any effect on these numbers, since egr only activates under a load. In CA, there is a functional check of the egr as part of the test.
 
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