Odd Thing With This Car
I noticed that if there's less than 4 gallons in the tank (18 gal. capacity) and I do NOT have the car parked on level ground, I can't get the car started unless I add a couple of gallons. I've already had the fuel pump replaced, so it isn't that. I guess it's just where the filler tube is positioned in the tank. So I cannot let my car go over 300 miles without filling up, because of this. My driveway at home isn't flat. The gas gauge on this car also does not work, so I can't actually participate in this experiment, but I did once drive it 410 miles on a tank, then put 17 gallons in.
Your pressure sensor needs to be replaced. It is located below the Power steering pump. You will need a 17mm wrench and some vaseline.
I've got a 2000 SLE too. I average about 24 mpg. Add to that the fact that I do need a tune-up and oil change.