krsone said:
Is the EGR modification/calibration necessary for the new 2009s? If so, how soon are you supposed to get this done before it does permanent damage?
In a way, I suppose a more general version of this question (i.e., "Can/should I modify the X?") should qualify as a FAQ here and get added to the list in post #1. The reasons I hesitate to do so are: (1) These cars are too new for anyone to have any solid, fact-based answers, and (2) My own personal answer is merely my opinion and doesn't deserve to end up sounding like a fact.
In case you're curious though, my own personal opinion is this: The '09+ design is so highly computerized, bristling with so many kinds of sensors we've never seen before (just one example: pressure-sensing glow plugs), all of which the ECU relies upon to make its decisions, there's a very high probability that any engine or drivetrain mods will have effects on ECU inputs that will deeply confuse your computer, throw a bunch of codes, and perhaps cause Very Bad Things to happen. As a rule of thumb, this is not a car suitable for modding, except for trivial stuff like adding a skidplate. For more functional types of mods proceed at your own risk (and, of course, kiss your warranty goodbye!). If one accepts this argument, it then follows that no modifications are "necessary".