A gas supply delivery arrangement of a plasma processing system for processing a substrate with gases introduced through at least first, second, and third gas injection zones comprises process gas supply inlets and tuning gas inlets. A mixing manifold comprises gas sticks in fluid communication with a process gas supply and tuning gas sticks in fluid communication with a tuning gas supply. A first gas outlet delivers gas to the first gas injection zone, a second gas outlet delivers gas to the second gas injection zone, and a third gas outlet delivers gas to the third gas injection zone. A gas splitter is in fluid communication with the mixing manifold, and includes a first valve arrangement which splits mixed gas exiting the mixing manifold into a first mixed gas supplied to the first gas outlet and a second mixed gas supplied to the second, and/or third gas outlets.