warric_k

check for injector leaks. I've had two cars in the last week come in with one or more leaky injector seals.

idiot-stick

Holy crap. I was about to brag on my 28mpg highway on my KA24DET. I calculated it during a 350mile ~90mph drive. The ECU seems to ignore the O2 after about 75mph in 5th gear so I tuned that spot to about 14.4:1

projekteg

get your ---- tuned and you'll get great gas mileage. i have my idle sitting at around 16.5 a/f, part throttle light load at about 15.5 and get 35+ mpg with my stock b16. i'm averaging almost 5 more miles to the gallon than with stock ecu. when i was boosted, i was a little richer in part throttle, mainly for tip in to boost b/c i was running closed loop on the ecu and would go in to boost sometimes at part throttle before the ecu would kick in to open loop, but even then i was getting 27-30+ mpg. it's all in the tuning.

sohc_mshue

you need to hook the o2 sensor up or tune your part throttle portion of the map otherwise your mpg will be shitty.