The turbin housing would most likely see a max egt of 1600*F. This heat would be dispursed over a large, even area. While im not saying it cant handle more, im saying you'll reduce the chance of it cracking if you put it in an oven or something of that nature. Because when cast iron is unevenly heated, it can cause it to warp and crack. Thats why I would advise you not to use a torch. Cast iron is pretty picky about thermal expansion.
Take your time, it will come off.
'96 Eclipse GS