When I have it wide open, it hesitates in the upper rpms, and then kicks in hard again. It does it in all the gears. I've run 2 tanks of injector cleaner through it. The car has 33k on it.(1997 Cobra)
the one and only time I ran injector cleaner through mine, it did that, sputtered a little around 5000 rpm's, than ok. I didn't have any symptoms to run it through, I had just used it in all of my other vehicles. my mechanic, said that we shouldn't need to use it on our cars, unless there is a problem. might want to burn up the gas you have, and run some good stuff through it, and see if it still acts up. mine stopped after the tank was gone. hopefully yours will also. good luck
I was running the injection cleaner because of the hesitation. According to the carfax on the car, It sat for awhile.
try replacing the fuel filter and see if it helps and try cleaning the MAF sensor. Could be something with the IMRC's too since its at WOT.