[nonovurbizniz]

the turbo creates all neccisarry back pressure for the engine. after that you want it breathing as free as possible there is NO such thing as TOO open for a turbo app. as long as the turbo isn't some kind of high end ball bearing high flow job on a small displacement engine.

As long as the turbo was on a car of a similar literage you won't need anymore backpressure than the turbo itself provides.