Im close to finishing my build up... full t4, e6k... ect.

Im looking to make as much power as possible.

current exhaust setup:
1.00 a/r ptrim hot side divided.
50mm WG
3" DP no cats
2.5" catback RSR

So i want to know how much the 2.5" catback will hold me back... is 3" a must?
My catback is pretty quiet and has 2 resonators in-line... so the sound of it is wonderful. I want to make sure its worth it to go with a loud *** 3" straight through.

 

With a turbo like that I would not be wasting my time with a 2.5" exhaust, and neither would I install a single exhaust if i was worried about having a "loud ***" system. A 3" pipe (with resonator) splitting into two big 2.5" mufflers (not weedy little cans) will flow just as well and not be too loud.