exhaust system after the header size needed

a 2000cc motor what is the recommended size some recommend 2.0" as the best period other recommend 2.25 and others say 2.5 if the motor is pumping approx.160- 175 at 7k what do you think how much of a difference is there and will there be a hole anywhere in the rpm band.I like to wind out hard not over rev the motor just like to peak the motor approx 5-600 over peak. running 1 5/8" headers 45 dcoes etc.I'm erring on the 2.25. anybody have a experienced opinion