Click here to enlarge Originally Posted by Ingeniator Click here to enlarge
Yeah for sure if your turbo is 2" outlet run 2" until the end tank. If it is 2.5" run 2.5" etc. Now twins should probably be roughly what Tony wants to run after the merge.
In the case of twins, After the merge I would run the same cross sectional area as before the merge, but rounded up 1/4" on the OD to account for turbulence in merging air. Those are my initial, untested thoughts anyway.