This is my regiment.
Twice a month I add a bottle of Supertech or Champion super concentrated Fuel injector cleaner. It's around 2 dollars a bottle at Walmart.
Every 3 or 4 months I add a Can of Berryman's B-12 to the tank. It's like 3 dollars and change, once again at wally world.
Twice a year, I add Seafoam which I used to only be able to get a Napa. Now it's available at Autozone, Adavance Auto and other stores. Cost is around 7 dollars and change a can.
BTW, Shame on me for forgetting to change the fuel filter when I bought my 'Tour. At the time, it had 60 some thousand miles. Now i'm almost at 123k, and I went under the car to change it and found it to be the original Ford factory filter.... Doh!