Exhaust opinions / Mandrel bent 2.5 or 3" / Input?

It will be a single system, from trans to bumper. I am considering the 3" to the muffler, and 2.5 out, but we will see. My gut says 3" to keep backpressure down as much as possible once the turbo is installed. The 3" may be way too much for NA but it forces me to follow through with the turbo....