2002 Durango SLT Acceleration Problem

I Have A 2002 Slt Durango W/ 40k Miles. Recently I Have Begun To Expierence A Problem In Stop & Go Traffic Where After About 40 Min. In Stop & Go Traffic When I Accelerate There Is A Lack Of Power Coming Out Of First Gear (automatic Tranny) I Have To Press Harder Than Normal On The Gas And When It Gets Up To About Third Gear It Will Correct Itself And Not Do It Again. I Have Changed The Tranny Fluid & Differential Fluid. I Have also replaced the valve body, govenor actuator switch, fan clutch, and output speed sensor. The dealer says he gets no error codes. No Fix Engine Lights Or Other Indicators Turn On. I Have Been To My Mechanic And Dealer, However The Car Does Not Do This Problem For Them. I Would Appreciate Any Suggestions.

only at low speeds and usually while turning, my 2002 40K miles durango stutters. acceleration is unsteady. this happens when i am parking or at traffic lights. the dealer put an additive in the oil and said it should be corrected within 2000 miles. i have done about 500 more since then and seen no improvement. we'll see what happens.