The below is from the file PJgamefaq (check your PJ64 folder). It was indeed in the FAQ for me
Why does the FPS drop to zero?
Do not enable Sync game to audio (default audio plugin) in this game.
Turok1, why can't I get into level4?
Some users find they need to use a Counter Factor of 1 (ROM Settings tab ) for this point in this game. Reboot ROM to take effect.
Turok runs perfectly for the most part, but you can't see the map with the default (Jabo) plugin. Glide64 shows the map, although if used with eVoodoo the wall and floor textures aren't correct like in Jabo's plugin.
Got it! Unchecked Force Depth Compare and Force Normal Blending; hopefully it should work properly all the way through. I'm also using a PAL rom now instead of the (U) version, would this be a cause for the problems?