Kind of +1 to Rayder, I believe someone did once try an actual overclock on the DS but that is a different matter entirely.
There are ways to hack games to speed them up but they would be done on a game by game basis, only a handful of methods might work on a given game, the games tend to be prone to crashing and is not always the easiest hack. You will not have seen it as a function of the cart unless the removal of AP happened to also speed it up (surprisingly common actually), the cart had a custom DMA setup for the game or some such which effectively sped it up a bit or in cases of things like saving.
Still the big three methods are
1) Disable vsync. The DS screen has a 60Hz refresh rate like the GBA before it so games will aim for a 60fps or 30fps framerate and you can stop this from happening. All sorts of weirdness can and does happen when you do this.
2) Soft optimisation. If things are animated you speed the animations up or trick it into thinking it is over, if you have 9 press a to continue after a battle screens you hack the game to skip to the end of the press a screens or combine it all into one. These are usually the best method from the game playing perspective as you do not need to actually do all that much and from the player perspective it is an amazingly effective hack.
3) Hard optimisation. Here you go down into the code and do all sorts of things to actually speed it up. This is probably one of the harder and less fruitful assembly hacks.
Few people will bother to make these hacks for you (they are not the least time consuming things out there) and furthermore if this is for pokemon then search around at the very least before asking as those that came before you did not make a good impression among those that might have the skills to do something.
Very short version. Consider what Rayder said as the complete truth as you will probably not find anybody that is willing to put the effort in to pull off such a hack.
