I have had my turbo for about 1 1/2 yrs, however, i have noticed im not getting as much mpg for the last couple of months.
-I had a spark plug tube seal leaking in the cylinder. fixed now and replace plug.
-i use to get 20 mpg in the warmer weather. Tested the other day 17 mpg now in cold weather. Same driving pattern though.
-My A/F ratio has increased it seems like it will hit in the 14's when cruising. Under acceleration is in the 12's.

Does weather affect mpg and air/fuel ratio? or do i have another problem?