Your problem sounds like it is the same problem I had. It took me 3 times taking it to the mechanic before he realized what it was. When full throttle in first gear at about 5.5k rpm it hesistated. The first time the mechanic replaced the fuel filter and that worked for one fill-up on gas. The problem returned and the mechanic didn't figure out what it was until the catalytic converter started vibrated, which was a sign that the fuel system was running too rich or lean and that excess fuel was being burned in the catalytic converter. So the fuel system cost me $370 installed (which fixed the problem) but since I have an aftermarket cat that is not under the federal 80k mile emissions warranty (because it is aftermarket) i'm being set back another $180 to replace it.
P.S. I was also having problems with the fuel gauge before the problem was fixed. It would fluctuate greatly when reading below 1/4 tank and it took a lot longer for the low fuel light to come on.
