I know this response is probably well after the fact, but may help someone else later.
Do you have to hold the ingition to "Start" for a longer period of time than normal before the engine catches also? Mine was having this problem and chased ghosts for a while before I took my brother's advice, who has been an auto mechanic for almost twenty years, and changed the fuel pressure regulator on the back side of the "spider" manifold assembly. He told me I'd be better off changing the whole assembly due to the hoses from the injectors getting brittle and breaking. I inspected mine and found them to still be flexible and chose not to change them due to the expense.
According to my brother, three of the symptoms can be poor gas milage, missing and hard starting.