Best MPG Tires for 2009 Prius

We had Bridgestone ecopias 422 on and my wife got around 50 mpg. recently we had to replace them and got the new version I think their called ecopia plus or 422 +, I don't know what the plus means but it doesn't help the mileage as right now I can't get more then 45mpg. Hopefully as they were in they may improve, also I didn't see where anyone mentioned about running a few more pounds of air at Costco they won't go above the set limit but you can increase the amount yourself but 2 or 3 lbs and it will help.