  The location of the Gamma-ray emission of powerful blazars is a matter of
active debate. Is the location within the UV emitting sub-pc scale broad line
region, or farther out at pc scales where the molecular torus IR emission
dominates? We present a diagnostic that connects three observables, the
synchrotron and external Compton peak frequencies and the Compton dominance
(the ratio of Compton to synchrotron luminosity) to the seed photon energy and
energy density. We discuss encouraging preliminary results and discuss how to
use our diagnostic to understand the location of the Gamma-ray emission as a
function of source power through the use of multiwavelength observations.
