Well, I don't know how many people have actually played that far into Y's 1&2 with an emulator, but since its a/the fan favorite TG-16 game, I'm pretty sure that the David & Cédric would have perfected it's compatibility years ago, so its probably the image you are using.
If you love the game so much, just spend the $20 or whatever on a legit copy and you'll have your answer.