I have had my TOG headers installed for over 4 years and not one leak.
Picking your muffler will depend on what kind of sound and restriction you want. Everything is a compromise between loud wide open high rpm power or muted part throttle low rpm torque.
My Magnaflows are the same as Borla or any other straight thru pipe with an insulated chamber. This type of muffler provides the least backpressure and does not change the sound of your engine, it only mutes it slightly.
It'* sound lost out by a group of very discerning Bonnefiles to the Chambered type like Rod Rounds has. The Chambered type like Hooker or Flowmaster provides a lower deeper pitch but because of the amount of deflection will absorb slightly more hp and weigh a little more for equiv size.
I like the sound of my Magnaflows on the SSEi. The buzzy high pitched staccato sound of a cold engine at low rpm can sound Ricerish but there is no mistaking the sound of the L67 at WOT high rpm when these puppies wail.