Stalling out when I slow down

For a while my car has been stalling when I slow down or about to slow down to reach a stop light. After googling the problem, I saw that the signs that I would see seemed to be the Throttle Body. Also a mechanic who I have went to for a while also said the problem sounds like its my throttle body. Any way, when the car shuts off I put it in neutral and restart the car and I have to press the gas or it wont start back up. I really needed to have this problem fixed and sadly the mechanic that I was preparing to take the car to closed down and now I have been stuck with this problem trying to fix it my self. So I ordered a used throttle body online and changed out the old one and the same problem is still happening. Could it be that the throttle body I just recieved is having the same exact problem as my old one or could there be something else cause this issue. I am still getting the same problems as before. PLEASE HELP ME OUT ASAP!