* Engine modifications: A stock engine will have different needs than one with performance modifications (intake, cam, etc.).
* Desired performance characteristics: Do you prioritize low-end torque, high-end horsepower, or a balance? A smaller diameter might favor low-end torque, while a larger diameter might favor high-end horsepower, but could sacrifice low-end.
* Exhaust system length and configuration: The overall length and bends of the exhaust system will affect back pressure and flow.
That said, a 1.5-inch to 1.75-inch diameter pipe is generally considered a good starting point for a stock or mildly modified 2.3L Ford Ranger. Going significantly larger without considering the rest of the exhaust system and engine modifications can actually *reduce* performance.
Recommendation: It's best to consult a professional exhaust shop. They can assess your specific needs and engine modifications to determine the optimal pipe diameter for your setup. Trying to determine this solely based on engine displacement can lead to suboptimal performance.