Trade Santonio Holmes for Bobby Engram?

Absolutely. Holmes is one of at least three or four targets for Roethlisberger and given the way Pittsburgh spreads their offense, not likely to be anything better than a flex spot WR on most weeks, if not a bencher. Given you have correctly evaluated your bye week situation, I think it should be clear that Engram is a good pickup for you. Plus you get the added bonus that he is not sharing catches with as many people. I'd worry about week 10 when it gets closer - you never know what injuries or fantasy sparks will come out of the woodwork. Good luck.