Pacquiao gained a lot of muscle since his fight with Marquez II. In that fight, he was 145, but that was after he hydrated from 130. Most of the weight was water-weight. Pacquiao was ripped at the 130 weigh-in, and he was ripped at the WW weigh-in's as well. On "paper" he only gained a few lbs, but if you compare his body before and after, there's a lot of muscle he put on in a very short period of time. From the JMM II fight to the Oscar fight. There's plenty of light-weights entering the ring at 147, but that is after hydrating. They don't suddenly gain 12lbs of muscle mass and enter the ring looking more ripped than natural WW's, just months later. Also, PED's are not just to gain weight. He could be on EPO or other PED's which would make him more relentless and with more stamina, etc.
Pacquaio himself can not win with your arguments. He is on PEDs, while facing a corpse of Dela Hoya, and shot versions of Hatton and Cotto.:good