Hi Albert,
That c'ant be a good sing when you smelling hot coolant, when you drove only in citytraffic!
I thinking only with change to a STi 1.3 bar radiator cap, your problem don't will be fixed!!!!
The problems is the shortblock from the EJ25, it was a EJ20 but overbored,!
Also the headgasket will be a low cost item, so this is the mean problem on these kind of engine...
regards
marcel