Unless you have the optional Sport seats, as far as I can tell from the parts diagram, the only difference is the colour, the part number is the same for 98-04, with no distinction on S or not.
They fit fine. Your hands will be sore and it take a while for wrinkles to settle out depending on your upholstery skill set. You get to pick the shape Nice thick leather too.
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Grant
Arctic Silver 2000 Boxster S - bought with a broken engine, back on the road with the engine replaced
Green 2000 Boxster 5-speed and 1978 928 auto
1987 924S 5-speed (Sold) - Blue 2000 Boxster 5 spd (Sold)