hahaha.........I would have thought so Nark but its not the only thing that would cause it. Maybe if a lot of people had this happen it could be an inherent fault in the design or something......All I know is it was an absolute b@stard of a thing to pull off the block 'cause it had warped sooooo much (and warped the heat shield 2). As for the shiney S/S one, if I had more time before the next track day I would have hunted an aftermarket one down but unfortunately I had to have the car back together ready for winton. Anyway managed to get my hands on a ported std item so should flow pretty well anyway.
Ash....thanks for the suggestion but my car has an a'market ecu etc etc and only got dyno'd recently so I know shes not running lean. Do have the req'd free flowing exhaust which helps but I'm thinking maybe when my manifold was match ported they could've shaved too much off in that area which led it to crack.