cadillo
Wiswin is right the fuel system could be the problem. I had a case where 2 of my injectors were causing the lean condition and it called for more fuel. I had already replaced the 2 upstream o2 sensors and put the old ones in the downstream. Be careful if you try to remove them because if they have not been removed before they can be hard to remove. When putting them back use some anti seize compound. If you still are troubled after the attemts mentioned find somewhere that will diagnose on the computer as I did when I had a hesitation problem. It should cost about $110. at the dealer. Just dont have them do the work if you fell you can do it yourself. I had an independant place do it and it worked out well. I replaced the injectors and finally the fuel pump. It runs fine now. 193,000 miles.