Same exact problem with me, except I have the hesitation at the 4000 rpm range. What's weird though is if when I hit this area, I take my foot off of the gas a little, the car will see the boost and go. But if I just floor it I'll sit at 4000 rpm's until I let off the gas. So I'm guessing airflow too because I changed my plugs, wires, and coil pack. The first time I changed all of these the problem went away, but it came back and when I changed them again to see if that was the problem, it didn't go away this time. Oh, and if it's the o2 sensor, wouldn't we get a cel? This does seem to be a huge problem for us. Someone figure it out!!!