Ford does take some steps to minimize back pressure, but BE CAREFUL. Backpressure is critical for power in the low RPMs. Replacing the whole exhaust will develop massive power in the 3000+ RPM range, but you will actually find there is a LOSS of HP and torque due to the lack of backpressure.
The best thing is just a cat-back system, and Pace Setter's V-6 adaptor. Try
www.pacesetterexhaust.com for more info.