There is a lot more experience in this thread than I have, but I will toss something out I ran into.

My suburban started running bad and I could see it in the data log it was running extremly lean and it was obviously much worse than yours is. I finally traced it down to one of the injectors being badly clogged and it wasn't flowing enough fuel. It was so bad you could see that one side wasn't like the other side. Both injectors were probably dirty and running lean, just one was really bad! I bought two new units and that fixed mine, if the chip doesn't fix that you might have dirty injector(s).