wow, that is hot! especially under those driving conditios you describe. i've just had similar problems with my wagon, i found i just needed another fan. my entire radiator is covered by a thick intercooler so that shouldn't make it get as high as you say.

basically i would have said to do all the things you have already done... it looks a little serious now how does your oil look? definately check your fan is going the right way, but if you have a 72 degree thermostat, when driving along there is enough airflow to keep it at a max of 80, without a fan altogether! is there a lot of space between you cooler and radiator? what about heat shielding from your turbo?