Midnight Club 3 : Dub Edition

[LunaMoo]

Difference in performance between drawing things and not drawing them is completely normal and not a "bug".

It's a Rockstar game so I would recommend disabling Vertex cache as it might help a lot, additionally try to lower/turn off any fancy settings you might use like high rendering res, texture scaling or even post processing shaders.
Vulkan backend can also make a huge difference in many of those more demanding games once buffered rendering get's completed, but if your gpu's are old you will not be able to use new api anyway.

While psp emulation is light, few games does require modern and fairy powerful hardware, each game is different - this is completely normal and ~ to finish this ~ again not a "bug".