I had insulation added to the walls in my house now the gas water heater
Fumes will not draft up the vent.

Your poor venting has nothing to do with installation of wall insulation. I would concentrate on the vent itself. First, check if the vent is not separated inside the wall, ceiling or attic. Make sure vent is not obstructed with debris and that you are using type "B" gas vent all the way through the roof. Single wall vent should be installed only between water heater and ceiling. But even here, "B" vent is highly recommended.