Too fast
If you're using Pete's GPU plugins, check off the 'Use FPS Limit' checkbox, and select 'FPS Limit (10-200)', and manually define your FPS limit, it is recommend you input 60fps for NTSC J and U/C games, and 50fps for PAL games. If you need a little speed boost, try incrementing the fps by a bit, maybe by 10 or so.
If you're using Lewpy's Glide GPU plugin, select the 'FrameRate Limit' option, choose 'Custom', and put 60fps for NTSC J and U/C, and 50fps for PAL. If you feel it's a bit slow, try boosting the speed a bit by incrementing the fps a bit, I suggest 10fps or so, but your mileage may vary.
If you're using Knack's Software GPU Plugin, select the 'fps limit only' option under the 'Framerate > Adjustment Type' menu. It's automatic, as far as I know, there's no way to customize it, yet