just an observation: is that flux (or crud) on the passives below the regulator on the right, or is that area burned?
Rule #1 check for voltages. A shorted supply line could pull the CPU/GPU down (if that's the case) and cause the system to report the YLOD? Possibly, I dunno. No experience with the PS3 topology. I would give the hardware a thorough look, ala Louis Rossman, before chalking up the reflow a failure, if it was even necessary to begin with. Good luck!!