2000 Ford F-650 Takes longer to start than it should

Most of the time I get in my truck it takes longer to start than it should. The starter is cranking engine too long before starting. Sometimes followed by a bogging sound that immediatly gose away. I am afraid I am going to ware out the starter. It dose not mater if the truck is cold are hot. This has been happening for years. It drives well once its running. Everytime I replace spark plugs they are dry and tan. My check engine light came on and checked codes. I replaced MAS and Oxy sensers, Air filter, Spark plugs, Plug wires, had injectors cleaned. I do not here any vacumb leak. Should I spend the money on an engine dionostic? I have not worked in 9 months.