2002 Dodge Neon Hessitation in going in late afternoon.

I recently relocated from Utah to Houston Tx. Since moving here I have noticed that my car hessitates when I try to start moving after being stopped at a stop light. It typically only does this in the late afternoons as i'm driving home with the air conditioning. I run the ac in the mornings as well, but it doesnt seem to have the same issues. When I press the gas, it will hessitate then go but move really sluggishly. Just crawling along yet the engin sounds like it is really reving. When I reach and switch off the AC it immediately picks up and starts going as normal. I have had all the belts replaced, the radiator and lines too. I have had the air filter changed thinking maybe it was a humidity issue. I am just grasping at straws at this point. Thanks for your help.