If you're sticking with stock turbo, go 2.5" all the way back, downpipe included. It'll give you a nice little kick and should increase torque.
“One thing I’ve noticed over the years is that if you drive into London at 6am, half of the cars on the roads are Porsches and Astons. Whereas if you go in at ten to nine, they’re all Renaults. Simple solution, then. You want a nice car? Get up earlier and do more work.”
— Jeremy Clarkson