My VY commodore has a stock engine was wondering will I gain anything if I were to install Mace ULTRA HIGH RATIO ROLLER ROCKERS FOR ECOTEC AND L67 V6?

With the 1.98:1 ratio rockers you'll be able to achieve gains of around 16 to 26kW. Please note as you have a VY V6, these rockers aren't suitable without modifying your cylinder heads We can however recommend our 1.9:1 ratio rockers with pushrods, achieving gains of around 13 to 16kw