My 2011 has the eco boost and I am very happy with it. The last 3 F-150's I owned had the 5.4 or equivalent and to me, the Eco boost came closer in feel to them than the 5 liter did. On the road, I am getting 20 MPG (4WD, super cab). In mixed driving, I average closer to 18. In town or towing...
I too have been using additives in the gas I use, but my ATV still needed service because it is not used regularly all year long. I have started biting the bullet/wallet and buying premium gas for my Bass boat and Kawasaki. More $$, but less than service, new fuel lines etc..
Just traded my 2007 Mustang for this 2013 premium V-6 with 6 speed tranny. The '07 was a great car, but this one is better in several ways. The 2011 F-150 does the heavier work