It sounds like you're discussing a specific car mod for (AC), specifically a 2004 Kia Optima that requires Custom Shaders Patch (CSP) version 1.16 or later.
If you're comparing the mod's performance to the real car's "solid report": 2004 KIA Optima for AC 1.16 CSP.rar
: Typically came with a smooth 2.4L 4-cylinder or a 2.7L V6. It sounds like you're discussing a specific car