The 90 may not flag every stupid emission error and may not be looking at EGR function. I had the idea of blanking mine but could never find out if the Euro spec 3.2 had them or how to bypass the detection method.

The only way to poll EGR to see if it is operating would be detection of RPM when pulsed. I read this somewhere but can't find it. I agree it doesn't make sense when driving as the throttle is always changing RPM. They described the method it uses EGR as pulsed not always just on or off. There was something like it checks every X amount of minutes when under run condition. Seemed like after a reset it took 2-3 days of driving to trip the CEL when not operating. It must not be too aggressive of a test.

Think about detection. There could be a switch on the EGR when the valve opens, the switch makes - none. Temp sensor at the EGR inlet on the intake sensing exhaust stream temp - nope. Could this be magic?