If I move the Sleep loop above the WinMMAudioRenderer Init call, CPU stays normal. Move the Sleep loop after the WinMMAudioRenderer Init call, CPU pegs 100%. My guess is that WinMMAudioRenderer is creating a thread that is spinning badly on something. Probably should submit this to premier.intel.com but thought I'd check the forum first. Thanks.
Discovered that the base audio renderer has a vm_time_sleep(0) spin on UMC_ERR_NOT_ENOUGH_BUFFERS. While no data is flowing through the audio renderer, this loop will peg the CPU at 100%. There are other examples of vm_time_sleep(0) or vm_time_sleep(TIME_TO_SLEEP) where TIME_TO_SLEEP=0 in other parts of UMC. They all need to be replaced with synchronization objects.