And here I go again - Goalie, before you go ordering parts, please - finish the mileage experiment. Don't do any math with the fuel gauge - it's only accurate to maybe +/- a quarter of a tank of gas, and you even said in a previous post that itt was showing only an eighth of a tank left, but only 11 gallons went in.
If you don't have the patience to wait until you finish this tank of gas, then go ahead and fill up now just like you did the last time when you reset the trip odometer and DO THE MATH... divide the number of miles showing on your odo by the number of gallons you just put in your tank, and that will tell you your true mileage. By the numbers you yourself posted before, you are getting over 19 mpg! (210 miles on 11 gallons of gas... 210/11 = 19.09).
Make sure you have a problem before you try to fix it. Problems that aren't really there have an annoying way of not responding to fixes.
Good luck!