The Mustang's OEM cats are pretty good high flow cats. Rather than make you replace them, this specially made X-pipe crossover can be added to your existing OEM catted downpipes by cutting the downpipes in the appropriate spot and slipping this X-pipe over the existing pipes. Stainless steel clamps and instructions are provided.
Brand new XFM43 X-pipe from Pypes
Fits all 2005-2010 Ford Mustang GT 4.6L
Installs after the catalytic converters; Street legal and no effect on emissions
Includes clamps to install to the front; Re-uses factory rear clamps
Features Pypes' lifetime warranty