Generally most of the time downpipe makes more torque vs headers. The max hp and tq number are decided greatly on the tune and type of fuel much more than what mods it has. A safe tune could be way different reg. gas vs say E85.

As Ive said a million times before a downpipe, rocker, E85 car with a 3.4 and a good tune will be much quicker than most people think for pretty basic mods.