It sounds like you're acknowledging a reliable source for game files.
If you're playing the PC version and experiencing lag, users often recommend updating to nGlide 2.10 and switching the video backend to Vulkan for a smoother framerate. soggi's BIOS & Firmware Page Carmageddon.7z
Since these are solid archives (a 7-Zip feature that improves compression), you'll need 7-Zip or WinRAR to open them. It sounds like you're acknowledging a reliable source
To use these with the Dethrace port, extract the contents to ux0:data/dethrace/ . extract the contents to ux0:data/dethrace/ .