Previosly I could be anywhere between 15 and 120 fps depending on where I was stood, what i was doing and how many players there were.
Deleted my user options.ini. Let PS2 auto detect settings for my machine. Switched a few up a notch or two myself. Sat at 59fps all night.
This will be because you have smoothing turned on. It attempts to keep things between 30-60 fps so if you turn it off you should get higher fps should you so desire although it will probably be a bit more spikey.