I have an issue with my 2000 dodge ram 5.2 4x4 1500. About 30 seconds after it is running "cold" you will here a vacume suction comming from the throttle body then it starts to run rough. when driving down the roan its seams fine under accel but when you level off in speed it stalls then if you let off the accel it comes back or if you press the accel it hessitates and then is fine as long as you keep accelling. I thought it was the intake gasket so I just changed the upper and lower gasket and it didn't help any suggestions???????????????????

 

Replace the pre-cat oxygen sensor. What you describe is the most common symptom of one that's dying.