You’re partly right about that YouTube clip being from the same play you are describing…only, Malkovitch’s character, Lee, describes a screenplay where one of its scenes is the two main guys are in a chase through the desert in their trucks. The trucks then run out of gas, but they have “conveniently” been hauling their horse trailers with them, and so they then get out on their horses to continue the chase. Lee is proposing this to his brother Austin, the actual screenwriter, who finds the whole story completely idiotic….but, Lee’s story is the one that interests the movie producer, Saul…funny stuff…