4 into 1 Mac header on a KZ550

No eBay APP ID and/or Cert ID defined in Kunena configurationI got a Mac 4 into 1 header awhile ago. It's just the header, no muffler or connecting pipe. My bike currently has stock carbs, airbox, exhaust and it is running great.
If I put this header on (with a muffler yet to be determined, but something with a baffle), what's the good and what's the bad?
How much tuning will the bike need if any? Any performance increases?
Was thinking about adding a Cone Engineering reverse cone shorty muffler.

Does this seem like a crazy good deal? Was thinking of making an offer, just to get the muffler.

If you leave the stock airbox and filter in place and only change the exhaust then you may not have drastic jetting problems.

That Kerker is a crazy good deal. You may want to grab that thing for the muffler. A local shop should be able to bend you up a mid pipe piece.

Kerker is always my first choice for a muffler. It'll be a little leaner, but you can probably use stock jetting with it.