When you are talking about the MAF are you meaning the plastic elbow pipe or the MAF sensor that screws into the plastic pipe OR both? If you replaced the plastic pipe then you may have a problem with it seating properly. If we are just talking about the Sensor that screws into the MAF a new Bosch may cure the problem BUT, If the car is idling that bad you should have a trouble code. Have you read DTCs ?? Go to any auto parts store and ask them to read the trouble codes BEFORE you buy any new parts.