This paper introduces several new component clustering techniques for the optimization of asynchronous systems. In particular, novel "Burst-Mode aware" restrictions are imposed to limit the cluster sizes and to ensure synthesizability. A new control specification language, CH, is also introduced which facilitates the manipulation and optimization of handshake control components. The new method has been fully integrated into a comprehensive asynchronous synthesis package, Balsa. Experimental results on several substantial design examples, including an 32-bit microprocessor core, indicate significant performance improvements for the optimized circuits.