Zacharia Farted (1998)

Uptight Michael and his new age buddy Brian take off on a road trip after Michael breaks up with his girlfriend and Brian loses his job. They find a mysterious unmarked headstone, with only a strange inscription and a key as clues. Brian instantly decides it is his life's mission to discover who is buried there, and the pair change plans. They find an Indian shaman who may be able to help with the inscription -- but he turns out to be a half-Apache from Belfast. Further adventures turn up a kleptomaniac waitress and, eventually, an old lady looking for her missing son. The group return to the gravestone.