With that said, if he has other stuff he can do to the car like suspension mods or a tuner or other bolt ons... that's better to do first. The stock manifolds really are not all that restrictive on the modular.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.