[Vwdiesel] TDI EGR-plugged manifolds

[Tony and Lillie]

So, we have been theorizing at work about these TDI's plugging up. We have had two recently, both very similar. One is a Jetta, one a New Beetle. They both have bad mass air flow meters. Well, we have been thinking maybe a bad mass air meter would indirectly cause the buildup. But, the uncertainty in our theory is, when exactly does the EGR open. The only thing we have in writing on the VW EGR is that it is controled but a vacuum solonoid (no kidding!) that is activated by the ECU. Also, it states that it can open in varying amounts based on cyclic opening.

So, does anyone know exactly what situation/s cause the EGR valve to be opened? Full throttle, closed and decel? 

Any help would be greatly appreciated.

Tony Hoffman