does this apply to an sps too - or do they have lightened one already?

They don't seem to have one for the SPS - I seem to recall being told that the SPS already had a lightweight flywheel and that adding one to my 996S engine would give it identical specs (apart from the injection and sensors). Could be wrong tho' - someone with more knowledge needed here.

SPS has a steel flywheel as standard.

It has a different one to the S as the SPS uses twin pickups for the P8 ECU, and S uses single pick ups for the 1.6M.

the SPS flywheel may be slightly lighter, but not by much and its simply because of its design, rather than designed to be lighter, if you know what i meen.?

There is a Ferrachi flywheel for the SPS with 4 steel inserts as pickups but the last time i ordered one it took ages to arrive (not much demand to make them i guess)