Once you have all the studs out that hold the upper manifold on to the lower manifold, lift the manifold and use a flat bladed screwdriver to release the electrical connector for the fuel injectors. The connector will stay with the injectors and the lower manifold. It may be a little stuck.
Right behind the throttle body is where the electrical connector is. There are 16 pins in this opening for the injectors. This connector is located at the arrow in the picture below. Lift up on the manifold while pushing down on this connector. There is a rubber seal around the connector that seals it to the upper manifold, so it can stick a little. Place a screwdriver in the area of the pins and push straight down.