I finally changed my plugs. My old plugs looked decent for having 40k miles on them. They were all gapped at 40-41. I replaced them with the Motorcraft 534's. It runs great. I notice a little more power and very noticeable is smoother idle. All new plugs gapped at 30. My question is what is the difference between original 2011 stock plugs in Eco and the newer Motorcraft 534's? By the way, changing the plugs was a very easy job. Plugs cost me a total of 39 dollars.

 

Platnium to Iridium I believe.

 

Just changing gap makes a difference too. Regaped my stock plugs down to 32 and MPG improved.
My stock plugs were 42-45...

 

Did same thing to my 5.0 Set gap on those to .044-.045 from .053