Build Your Own Sandwich

Standard sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9. Modular lines: every set of three adjacent digits along a modular line must contain digits with three different remainders when divided by 3. Sandwich sums: numbers outside the grid indicate the sum of all cells between 1 and 9 in that row or column, excluding 1 and 9 from the sum. Every sandwich, including the crust, forms a hidden modular line. For example, a sandwich clue of 8 could be made of the three cells 189 but could not be 1269.