GSC Power-Division S2 (duration 272) cams are designed for those with a GT35-GT37 turbo, and are not suggested for those running smaller than a stock appearing turbo (see the S1 cams). These cams are great for 2.0L engines revving to 9000rpms or for Stroker motors revving to 8000rpms. The S2 cams do require upgraded valve springs.
GSC Power-Division S3 cams (280 duration) are designed for those with 1000whp+ applications, and are recommended to used with large turbo applications. These cams are NOT recommended for anyone running smaller than a GT42R turbo.