Burns mufflers come from a company named coast fab, they're not much cheaper but you can get a lot more sizes off the shelf.
and stainlesssteelheaders.com sucks.
They were trying to have them do the GTR headers while I was at Boost Logic, they don't clean the bends, they don't back purge, undercut welds, over heated, under heated offset and slash cut tubing. looked like 60 amps on the head flange to runners. It was literally a list of shit not to do on a manifold.
Worst manifold i've seen in person is the Kings Performance S2000 manifold. it seriously looks like they use like 2cfm of shielding flow.