My 08 has the two converters in the Y-pipe, A large muffler and a resonator near the rear axle. No resonator before the muffler and no 3rd converter. It's all 3" behind the Y-pipe and flows good from watching the condensation in the mornings. I'm gonna leave mine alone for awhile. I had a Magnaflow 3" in, two 2.5" out on my old 01 F150 and it sounded good, but I can hear the MDS drone in the stock exhaust and would rather have the added MPG's over the annoying drone and always using the tow/haul mode to cancel the MDS function.

 

i have an 04 1500 SLT, i was hoping to put headers and real dual exhaust (not hi jacking thread just adding), would that mean you need double the amount of o2 sensors and cats? then you would need to play with the computer right?

 

No, you can use the headers, 1 converter per side, and use the same number of 02 sensors. Should be one before and after each converter.