No. I distinctly remember the two “Mythbusters” guys, esp. the guy with the quasi-handlebar moustache. He’s hard to miss. Also, it was just the two of them, mostly, on camera. It was definitely “Mythbusters.” Sorry you guys can’t track it down, but it’s out there.
I also searched around online, but found nothing.
Searching through the 'official' Mythbusters Encylclopedia of Myths for keywords, 'TWA 800' or 'kerosene' returns nothing.
Searching for '747' returned two episodes (#90) about whether a real 747 could blow a car off the runway and whether someone with no flight training could safely land a 747 (#94).
Searching for 'gas tank' returned one episode (#88) about the various myths surrounding gas tanks in cars.
Not a flame, but since you mis-remembered the altitude of TWA 800, it stands to reason that you might also be mis-remembering this, too.