Intake valve closing in the most important valve event.
Close it early and low rpm torque is up but high rpm breathing/HP is limited.
Close it late and low rpm torque is down but high rpm HP figures go up.
With late closing, compression can be increase because effective c/r is low at low rpm.
With state of the art ECU, fuel & ignition timing can be such that a late closing intake can still have good low rpm grunt.