I have a 2014 Jetta TDI, and the thing I'm wondering is what the cost of the fix will be - not to me in dollars, since it would be covered by the recall - but r

I have a 2014 Jetta TDI, and the thing I'm wondering is what the cost of the fix will be - not to me in dollars, since it would be covered by the recall - but rather, will this affect my fuel economy or performance in some other way? I'm just trying to figure out why they don't have the cars running in this lower-emissions mode all the time.