For a month I've been trying to find the vacuum hiss and gas smell in the 80 shortbed. It hissed for about a minute after shut down, and everyone said it smelled like gas(my smeller isn't so good). I finally got pissed and started prying on stuff after a 1 mile drive.....over and over. Turns out the fuel line rubbed on the header so long......it wore through and was leaking gas on the header. I never found the leak because the gas was cooking off. I got in a friendly arguement with a buddy once about how hard it is to light up gas.......