ERROR CODES FOR JDM OR ANY GALANT 1997 & ABOVE

Right now i`m looking for some reasons why my fuel consumption is sooo very low like 320 km to 335 or so to a full tank of un-leaded gas.Now i do alot of short runs but that shit still still not right .I changed plugs today next i hope to service my injectors any help will be appreciated. Then i`m hoping to locate a gas filter for my 1997 japaneese VRG galant to purchase. But i`m thinking that my air sensor is faulty & in my country TRINIDAD & TOBAGO the firm don`t support foreign used vehicles & they are the only one with the correct tools & they don`t have the error codes for my car so PRESSURE!!!!!!!!!!!!!!!!!!