yes this is interesting, i'm inthe same boat as u thai. but not as much? i always ran a pipe for cold air somewhat, but since changing to trd and the ported headers, my best fuel efficiency on caltex vortex 98 was 8.18L/100km. i'm now trying BP ultimate for 1 month and see how that goes... then shell v power, then back to caltex... i found that i get more mileage with the caltex vortex more than any other fuel, with these ported headers, that MIGHT change... edit: rememeber, no lifting and shifting at 3.0 to 3.5k