Use This Emulator instead.
It is GPsp 0.9, it runs most games at full speed, much faster than PSPVBA (Which the author, zx-81, stopped working on when GPsp was released).
You really shouldn't expect perfection in an emulated game, especially when your emulating a modern system.
Its normally not a matter of a config file, but that the emulator is not full speed. The author may update it at some time, they may not.
EDIT: Theres a tip on how to find the correct bios file in the installation instructions on the download page.