Place the fresh mango and lime juice in a blender. Blend until totally pureed and smooth. It will be a bit thick! If it looks waaaay too thick, you can add some extra lime juice, but remember we will mix it with all the booze and soda.
In a large pitcher, stir together the mango puree, tequila, grand marnier, mint syrup and club soda. Add a few lime slices and some big handfuls of fresh mint. Stir. Taste and if needed, add more mint syrup and lime juice. Or tequila! Everyone likes their margaritas differently.
To serve, stir together the sugar, salt and chili powder. Rim a glass with a lime wedge and dip it in the chili salt. Fill the glass with ice and pour the punch in! Enjoy.