I have to say, I am surprised by how bad MPG you guys keep getting! I know the Mach 1's and Cobra's will get worse MPG than us GT owners, but still, 14-16 MPG? Is that all city driving? My driving is a good mix between city and highway, about 50/50. My only mods are an O/R H-pipe and the IAC mod, and yet I get about 20 MPG no problem with my auto, and that is not babying it. The following tune-up items have less than 10k miles on them: Fuel filter, spark plugs, coolant fluid, transmission oil, engine oil, gear oil. The fuel filter is in decent condition. I ran half a bottle of sea foam through my IAC vacuum line, and the rest in a full tank of gas.
2003 Mustang GT
Intake & Exhaust: K&N FIPK CAI, Mac O/R H-Pipe, Custom Catback w/ Magnaflow Magnapack Mufflers.
Suspension: H&R Super Sport Springs, KONI STR.T Shocks & Struts, J&M Caster Camber Plates, Steeda Bumpsteer Kit, UPR Elite LCA's & UCA's.
Performance: BAMA 93R Custom Tune, FRPP 4.10 Gears w/ Terminator spec T-Lok.
Planned Mods: FLSFC, Eibach Sway Bars, Throttle Body, Plenum, Rims.