So went ahead and did the gray tank vent this weekend. Found the same issue, not as bad, as I had with the black tank vent, I snapped a few pics this time to show you what I was dealing with. The picture in the link below doesn't really show the bigger issue, which is I could see inside the camper from the roof once I took the cap off, it was the same with the black tank vent. Also, I know I need to clean up the roof, it's on my list of to dos before the season.
This camping season should be a much better experience for our noses :)!
Gray Vent