your getting the same as I am and mines not stock is my point. Disabling the sc will cause an air restriction so it shouldn't help (you have to get air past the rotors that are no longer spinning)
I am getting 31 mpg's on the highway and with the belt on in the city it was 27.2 mpg's and without the belt on it went to 29.4 mpg's, you stated you were getting 23 mpg's. I don't know how that's the same. I was only stating my experience.