dont understand why

This is just one of the million bugs the emulator has,just wait for next releases

Heh no matter what kind of specs you have,you wont be able to play games at good speeds(20fps at most ingame) yet.Also pcsx2 has to be reprogrammed to make use of 2 processors,so you wont get any speed increase from those
The error you get obviously has no relation with your specs

Im quite sure that it can mess up the emulator quite a bit...so you better not post it here

If it doesnt make the emulator run faster why did you say the fps rose from 20 to 80? You mean just the displayed fps and not the real ones?
Anyway i dont see what you want to know about the fifos error,its a bug...for further details you will either have to see the source yourself or hope(rather unlikely) that one of the authors will take his time and explain it

Glad i could be of help..hopefully ill find a game that has the bug you mention and debug with the authors to fix it