Every kit minus the Borla is 2.5", the stock manifolds on a modular aren't restrictive like the pushrod headers are. You'll be fine.
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 ****.