The mysterious noice problem. I have had a few of those. I remember once I had one. Often I have gotten them and it was a matter of cleaning, lubing and tighting the bolts on the chain rings. Some times it can be two spokes rubbing together (but with the new wheels, I don't think so). One time I had it and did everything I could think of and it drove me nuts! It turned out to be a hairline crack in the water bottle cage which only creaked on the power stroke on one side! Good luck.