Maybe snow is blowing into the muffler? Even so, after 20 minutes of driving, it should be hot enough to not only melt, but vaporize any water and expel it out as water vapor.
Do you only do short trips? (less than 15 minutes)
Curious how they drained the exhaust. Ask them if they removed it or did they tip the front end of your car up? :- p
Do you only do short trips? (less than 15 minutes)
Curious how they drained the exhaust. Ask them if they removed it or did they tip the front end of your car up? :- p