Hey I'm looking at replacing front to back my ehaust set up. I want a subtle deep throat to it... not loud and obnoxious... looking at a borla muffler for the end a 4-2-1 header is on its way. Next question... what size of piping should i use? This is the first mod but by no means will it be the last. I dont want to remove too much pressure but i dont wanna end up ripping it all off later. Also for a subtle more quiet tone should a high flow cat and resonator be tossed in the mix? let me know what you think. Thanks.

I would check for a catback system offered by your header manufacturer , it would be polished stainless steel with an included resonator , probably 2.25" maybe 2.5" piping . That's plenty big enough if your staying n/a otherwise custom fab 3" if you intend to turbo the engine . Definitely a magnaflow high-flow cat should be added to those headers to replace their 'test pipe' . If it's too noisy change out the resonator for a magnaflow that's a common issue .