Where did you hear that SS manis didnt crack? Stainless Steel is the 3rd most emmorphous elements in the world. And Cast Iron will not melt under turbocharged conditions. I would give any SS manifold 10K - 12K miles before they crack. Sure they flow better cars that arent daily driven. And what really sux is the fact since they morph(change grow strech etc...) so much the more you brace it the more they are prone to crack. CAST IRON is the best manifold for street daily driven cars IMHO SS is so overrated... Like Sabri said coat the cast iron and port the shit out of it you will flow the same and still have reliability.