Admittedly, I didn't read ALL the replies to this thread, but you dodn't mention anything about replacing the O2 sensors ot the temp sensor.

As I said, I didn't read all the replies in detail, so maybe I missed it. The temp sensor made a big difference in my initial start-up. It is also pretty cheap and easy to replace. Your cars computer could be reading a "warm" signal until it is warmed up a bit. This will make it run lean until you get closer to operating temperature. I think I paid $15 for the sensor. Also, the O2 sensors may not be up to par. If they are reacting slow from being old, you could also experience a hesitation.

Just a few random thoughts.