I wonder if they changed the ecm tune from yours being very early production, my 15 is an April 15 production date so nearly at the end and mine has always been 22 to start, one time as I recall 23. I am on the recall retune at about 3000 miles and it changed my regens to 800 miles plus with mixed driving and it was much shorter than that before. So far the recall has been a good thing for me. I wasn't too concerned about getting recall done around 21k miles since I was under full warranty.