One interesting change is I put it in reverse in my driveway, which is uphill, it now moves on its own without any accelerator pedal. It never did that before. That would seem to indicate that its generating more power at idle than before. I don't have enough miles yet to see if there is any fuel economy improvement.

Here is an observation since installing the aero-turbine muffler. The exhaust note is lower while idling.... however, several times I've noticed that the low note was gone and it sounded just like the stock muffler. So I was letting the CRD do its turbo cool down and decided to listen to the exhaust sound. After about a minute, the lower note sound stopped, it became quiet and the amount of exhaust increased. I tested this several times over the last week. Once I pull into my driveway, around 60 seconds of idle time and the low note goes away, sound gets quieter and exhaust gas amount increases. This is repeatable.

I experiemented with the turbo vacuum control and found that by disconecting the vacuum line from the vacuum boost tank, the sound goes back to lower note - put the vacuum line back on and it quiets down. Several quick iterations of this and the sound immediately varys between low note and quiet again. It appears that the position of the VGT vanes are changing the idle sound characteristic.