I'm suprised your not getting better mpg.
I have a manual shift 06 mazda 5 with the non turbo version of the same 2.3 you have, in a even bigger and heavier car. Despite this, my worst tank ever is around 26 and normally I see more like 28 or 29 around town with 30-32 on hwy trips.
All I do to get these numbers on the hwy is use the cruise control and don't speed, and around town I acclerate briskly but short shift, ( as much as I can without lugging the motor) and again no speeding.
I am unsure why you car doesn't do better, it sounds like your doing everything right.