They actually did have an answer to &quot;How did you do it?&quot;<p>The idea was that only DEP and EGR was needed for the smaller TDIs simply because they burned less fuel so produced less emissions across the board. That&#x27;s not enough to meet current limits, but VW claimed they had better CDI that solved it. They got many patents related to that and other companies even licensed it. But how did they get such good performance, the lines was due to the turbo and the tests did not really spool that all that much.<p>Turns-out it was baloney, but that&#x27;s how they explained it at least.