Tom from Yorba Linda

I have this identical problem, but I don't think it's a fuel gauge sending unit problem. Sure, my car runs out of gas at 1/8th tank, sometimes within 2-3 miles of the warning light coming on, and sometimes even before the warning light comes on. But here's the strange thing, the tank is a 19gal tank and I'm running out of gas when I've used ~14gal of gas. I rarely pumped more than 15 gallons into my car, yet it's got a 19gal tank. Over the last couple years I've been filling up at 1/4 tank because it's getting worse, but I'm usually pumping 12 to 13gal of gas. So the sending unit seems accurate. For some strange reason my car starts bucking and spitting, like I'm running out of gas around 1/8 tank, or about 13gal down. After I fill up the car runs OK. So I'm wondering if anyone else has pumped more than 15Gal into their 1998 Lexus GS300. I'm wondering if the 19gal spec in my manual is a misprint, of if my fuel system has a problem, like maybe something in the tank blocking flow, or an air leak in the pickup, etc. I would expect this car should go another 50mi AFTER the warning light comes on, like other cars. If I "space out" and see my gas warning light come on, I'm at the next station IMMEDIATELY because I know I'm terminal if I don't. My light is more like a 1mi warning light, if that.