Maybe I'm biased because I have one, but it seems to me that the S12 series would be a great car to tune. And yet no one does. Why is this?

I have one and Ima put a VG30et init HEHE:smoker2:its a nice ride and very capable. Its unfortunate no one tunes them

I think these are sweet little cars, but so far no one has shared my enthusiasm. They're just ripe for an engine swap! :D

There's actually quite a few S12 enthusiasts around, including myself. Check out my 200SX site (http://www.angelfire.com/80s/tsi200sx) .
Also, on the Links page, there's links to great resource including the Club S12 Forum.