I just bought my 99 subie turbo a month ago and about a week ago i encountered this engine heating problem. The weird thing is, the temperature only starts to rise to the very top of the engine temp gauge when im driving it on a snowy track going sideways a lot, or sometimes on a deeper snow and this happened 3 times already. First time i saw that, it took only about a minute of slow straight line driving and the temperature once again was fine. I guess there wasnt enough air taken through scoop on the bonnet. Note: im not having this problem while driving as i usually do in public streets, or while having a lil drag race or w/e. I thought head gasket, but it seems weird that the engine only starts to heat up when im really "stepping on it" in a track or tryin to do some basic sliding on a wet parking lot or w/e. btw, i had some fun on snowy public roads before and everything worked as a charm, no problem with the heating at all.
thanks in advance