h stood for high compression, higher compression was part of the update from b to h engine. it continued in use in the 900/9-3, 9000, and 9-5. the 2003 gm epsilon-based 9-3 switched to the gm ecotec engine, leaving the 9-5 as the sole user of the h engine. the last model year for this family of engines was 2009. the tooling and know-how was sold to baic.