MIVEC on the Evos was inlet only for the 9 and twin on the 10.

A lot of the reasoning for it is purely to satisfy the emissions laws and keep the green folk happy. Yet still allowing performance at the top end. Has the added bonus of improving drivability/powerbands/response as well.

However, think how much it costs to bolt a pulley to the end of a cam. Now think how much it costs to develop an adjustable centre to that pulley, create a failproof system to adjust it, control it, evolve it, map all possible combinations extensively etc. Ask yourself if you were a car manufacturer - would you pursue it?