Slight Hesitation / Loss of Power

Hi, I have a 96 Corolla (5 speed) and sometimes I feel this slight miss or drop out when I'm driving at a constant speed. It is really only noticeable at slower speeds (50 - 70 km/h) and not on the highway. I posted before with similiar problems that were more severe and a new coil seemed to fix that. Other things I have changed recently are: spark plugs (densos), plug wires, fuel filter, air filter, and I've had the injectors cleaned with a motorvac. I've ran different grades of gas and there was no difference. The only codes the check light turned up was one for the rear O2 sensor and one for the air intake temp circuit - could one of those cause trouble related to this? Other than that the car runs excellent and I get good mileage for kind of stop and go driving I do. Thanks for any suggestions!