All of the "f" emulators are written by the amazing rlyeh. While I haven't actually looked at the auto-frameskip code, I am guessing it doesn't go below 0 for the frameskip. This means that portions of the game which has unusually high FPS will cause the game to seem to run "too fast". Additionally, FS is only an approximate - it still may cause some parts of the game to run too slow. I'm pretty sure the math used for auto-FS isn't TOO complex, since the more complex the math, the more time it takes to compute. If the emulator has an overclocking option, try setting it higher then 133MHz and using FS 0 all the time. You can't expect emulators written for a handheld to run like they would on a desktop computer - the GP32 doesn't even have 1/10th of the processing power of the average desktop.