Camry hesitates

I have a 2000 Toyota Camry LE V6 with 115,000 miles. It's an automatic, 2 wheel drive. Lately, whenever I run the air conditioning, the car hesitates. When accelerating from a stop the engine chugs until I pick up speed, and at around 45 mph, you feel the same hesitation/chugging. At other speeds, the hesitation isn't noticeable. When the A/C is off, there is still some hesitation, but not as bad as when the A/C is on. I had the car tune-up at 60K miles and I've had the fuel injectors cleaned recently. I also changed the air filter last week, but the problem continues.

Thanks for your help!