Really? I think that the T25 inlet has a more round hole. T3 more of a rectangular shape, and T4 more of a square shaped hole. But yeah check the ID number and that will better tell you what it is. And no, a DSM J-pipe will not work. They all have a diamond two-bolt flange, not three. You could, however, cut and weld a DSM J-pipe to a three-bolt outlet flange.