GS300noob

iTrader: (1)

i know there are a few threads about the fuel tank / floater issues and gas running out at 1/4 tank on here, but i think my issue is a bit different. the toyota dealership installed a Napa fuel pump , and at the time of install , my gas tank had about 1/8th in it ( the E light was gonna come on any second) ,, then when i picked my car up from them , i noticed that my fuel gauge was 1/8 above the 1/4 mark. so it gained 1/4 tank .. i drove around for a day or 2 , and noticed that the gauged was not dropping as fast as it should. i filled up when the gauge was a hair above 1/4 and i put in 18gallons. so i went back to the dealership and told them about the issue, they are going to look at it/try to fix it on Wendsday at no charge, but i was looking to get some info/advice on what to suggest to the service center on what the issue might be. 99 gs300