True dual 3"?

[sethchid]

Hey guys, new to the forum, and glad to be here! I have a 2005 SuperCrew FX4 with the 5.4L, K&N CAI, SI/DO flowmaster 40 series and soon to be installed Gryphon and I'm looking at getting a set of pacesetter log tube headers, magnaflow highflow cats, dynamax race bullets and an "H" pipe. The headers have a 3" collector on them so my question is this: Should I get the 3" magnaflow highflow cats and keep it 3" to the back or should I reduce down to 2.5" before or after the cats instead?