Yes, the steel frame has a mixture of certain welded-together pieces being high-strength steel, with other welded together areas being lower strength. And there may even be mid-strength steel components also. There is somewhere a graphic which has the different areas color-coded, which perhaps someone will be able to find online, and link, and my memory of this is what I base these statements on. I believe the high-strength steel areas include at least some portion of the a-pillars, for example.
Edit: although it's a 987 ( 2006 model ), here's a picture showing the different alloys used in the different areas of the steel frame. I think it's likely that the 986 isn't too far off from the 987 design:
