How do you know they are running too fast? I have played a lot of pcengine games and none ran too fast, a lot ran too slow though, try them on a pcengine emulator for the pc and compare. If you really want to slow it down go into options and choose the 60 fps option, thats 0 fs and will slow it down quite a bit.
I don't think I have played any games on the pcengine that run full speed at 0 fs, what is it you are playing? And did you emulate it on the pc to compare? If it slows down when you fire that means there is slow down therefore it runs slower than full speed when you fire rather than it running faster than full speed when you don't.
arrr i want a new version of gpengine!!! I want to have a save option !!! plz!!
my games a running all perfect. but street fighter II has some sprite bugs.
My gpengine is running with 160 mhz and 30 fps. don't know if its the real speed but its good playable and its fun.