The original manifolds they created were stainless (right?). They cracked obviously and he had to switch to Inconel as a metal. Inconel, while being very strong, is also subject to some of the same problems stainless is (right?), so this is why they added the flex joints to insure you WONT ever have cracking like other companies manifolds which always crack.
When I get another Z, I am going to Gregs shop (all of 4 minutes from my house) and dropping $1,895.00 +install on manifolds. Thats just the way I see it.