Peng Problems is a side quest in the Orient (Act III). It is given by Zi Chan, a young guard captain standing near the western Rebirth Fountain on the Great Wall. He will tell you of a 'giant peng' blocking the way along the Great Wall. Just follow the Great Wall to the east to find a larger Peng named Xiao - Colossal Peng. He's basically a stronger version of a Razorclaw Peng and uses the same mid ranged Sonic Wave attack. In addition, he occasionally summons a few Gibbering Pengs. You can also talk to Zi Chan again to get some updated dialog from him, but this won't complete the quest.