I have some info on this topic, 3 aspects to look at. First, a full tank of gas has less room in the tank for air, so more pressure is built up along the rail, if you measeure FP on an empty tank of gas, at 2000 RPM, you should read between 32-37 PSI, on a full tank of gas you chould read between 35-39 PSI. at WOT PSI on first gen; not sure about other gens; should read 43PSI. SECOND thing is Volitility, rate at which the fuel evaporates, on a full tank, its all fresh gas still full of certain "substances" that your car thrives off of, in a tank thats a few days old, those "substances" evaporated and you can notice a "lack of power". THIRD thing is a feeling a Eurphoria.... after you feel up your car, you feel good about yourself, like its one less thing you have to worry about..... so as you pull out of the station and hit the throttle, your car feels like the <u>fastest car in the world</u>(feeling may not apply to all). Also when you have a low tank of gas, most people useally "baby" their throttle to save some gas before the next fill up..... Anyways, between all 3 of those aspects, differences in the quantity of fuel level may seem like a big difference.

 

well, i agree with the fact that the pressure might be higher and the feeling of havin a full tank of gas..... but i didnt butt dyno it, i went to the track with different levels of gas in my tank and my best runs were on E smile.gif