Only problem is, I'm getting a lot of slowdown when theres a few objects on screen. Is that an emulation problem?
I hope this is only an emulator issue. It should be. Unless your version of DeSmuME is different from mine, it should display the frame-per-second in the title bar. If you see it falling below 60fps, then it means the emulator cannot keep the pace. maybe you can disable scaling / anti-aliasing to get more FPS.
If it sticks at 60fps but you still have slow downs, then there's an issue with the game engine itself, and I'll have to look into it (and then, it would be helpful if you can snapshot a few places in the level where it happens).