Ok, I own a 1998 Nissan Skyline HR34, or R34 GT. It obviously has a RB20DE after that being said, but my car has an interesting fuel problem. So my car has an A/T switch, in regular mode the car uses gas like it's no one's business. Like just about a regular 15 minute drive, no autobahn or anything, will use a bit less than a quarter tank! I didn't see my engine temp shoot up or anything so I don't think it's running too lean.. but then I put the car is eco mode. (A/T in the down position, A/T switch turns green) now the car barely uses any fuel at all! Got lost the other day, drove around for about 20 mins and the fuel gauge didn't even drop. But after about an hour or 2 I noticed a drop in fuel obviously lol but it wasn't much at all. Why does it do this? I've yet to try out power mode in the car (A/T switched in upward position, A/T switch turns red) when I get my alignment done I will try out power mode. Any suggestions as to how I can fix this? If I have to run the car in eco mode for the rest of the time I have it, then so be it. But this problem is kind of annoying, sorry for the long read, any help is appreciated. Thanks!