The sum of the cages without a sum is given by the 2 digits in the same box, in the oval (but off by 2 - if x is the 2 digit number in the oval, the sum is either x+2 or x-2).
All the cages have odd sums.
The little killer on box 7 has the same sum as the two digit number in the oval in that box.
Three nines sit on one of the major diagonals and three fours on the other.
Normal sudoku rules apply, and the cages do not have repeated digits.
Solve the puzzle online at f-puzzles
Solution code: Enter the digits from row 2 and then column 8