Geoffrey Bower (ASIAA) Intensity Mapping of High Redshift Molecular Gas Molecular gas is an important probe of galaxy evolution and the growth of structure throughout the history of the Universe. Large interferometric arrays such as ALMA and the VLA are providing powerful insights into the most massive and most luminous of these objects. But the bulk of galaxies and molecular gas will remain undetected by these telescopes. The technique of intensity mapping can provide a statistical detection of the integrated luminosity function of all galaxies through low resolution mapping. We have recently analyzed over 1000 hours of observations with the Sunyaev-Zeldovic Array, setting the strongest limits yet on the molecular gas content at redshift 3. We are also planning new observations making use of the YT Lee Array (formerly known as AMiBA). The YTLA is a 13-element millimeter wavelength interferometer located on Mauna Loa. I will describe why the YTLA is ideal for these measurements and the technical development of a digital correlator and new intermediate frequency system that will make intensity mapping possible.