Hello, and thank you for allowing me the opportunity to help you. If I am not online when you are, please allow me time to return. Can you tell me how many miles are on the engine? How does the vehicle run at higher speeds?
Okay. It sounds like you may have a bad or dirty EGR valve or a vacuum leak. Before going with that though the easiest place to start would be to clean out the throttle body. If the throttle bore and plate are dirty then the vehicle will act like this. You need to remove the air intake tube and spray out the throttle body with throttle body cleaner. Then wipe it out with a clean rag paying close attention to the cleanliness of the throttle plate.