Pre remap was thinking of upgrading to a 3" system - i have a 2.5" turboback already fitted

Looking around at various systems there's the obvious ones like the NurSpec however it cones down to 2.5" at the downpipe - so is it a true 3" system in terms of performance?

 

You will need to cut the end of where it narrows down and weld a piece of 3inch pipe and flange. Then it will be a true 3inch.
I'm looking at doing the same as the blitz flows well.