Question Camry '02 V6 engine hesitating

[giovanni]

Does anyone else have this problem?
It started 6 months ago when I noticed engine hesitating on highway at speeds above 60 mph when decreasing the thortle to a point that is not accelerating nor decelerating (trying to maintain a constant speed).
After notifying the dealer and hooking the car to the electronic tester, there was no indication of malfunction other than a couple of misfires on pistons 5 & 6.
I did some research and disassemble the throtle body. It was full with deposits. The buterfly at its closed position would not allow any air passage. After cleaning, the hesitating went away.
Recenltly the car start hesistaing again. I checked the throtle body and is clean. I also start using syntetic oil. Car has 135k miles, I am the first owner, the engine check light is off. Dealer replaced spark plugs and I replaced the PCV. Oil was changed by myself at 3k intervals.
Any advice is appreciated. Don't know what else to do. Don't want to sell the car. It is in good overall condition.