[BRugNY]

I have never done a heater core on an SVX but have on a few imports and like previously stated that should be a LAST resort unless you want your car off the road for good period of time. I don't know if they have a cabin air filter but that could have something to do with it. Maybe you could try blowing out your air ducts with some compressed air. It could break loose any unwanted mess in there. But the fog would indicate some moisture getting in the system from where. Hopefully its nothing too serious.