Does the Stage 2 chip works well or would I need to buy an aftermarket ECU? as I have been told the standard VS ecotec computer are not good for tuning,provided Mace don’t offer stage 3 cam with a chip.

The Stage 3 COMP Cam with the memcal from the Stage 2 COMP Cam memcal would still be drivable, however you'd requre a custom tune. You could get an aftermarket computer, however the factory computer is more then capable if recalibrated to suit this cam.