57th episode of Miami Vice — Diehl made his last appearance in a two-part episode, "Down for the Count", in which his character was killed off. Diehl moved into a basement apartment in Greenwich Village in New York, and despite a drastic reduction in his income, he declined television roles, and chose instead to continue working in film while pursuing a serious stage career. He subsequently appeared in The Hanoi Hilton (1987), a film about the experiences of American prisoners of war in Hanoi in the 1960s/70s, and Alex Cox's Walker (1987), which was shot in Nicaragua during the Contra War. In late 1988, Diehl relocated to Los Angeles after he was cast in Sam Shepard's A Lie of the Mind at the Mark Taper Forum. He continued to work in theater in New York, however, and frequently returned to the stage there, most notably for a Shepherd play at the Public Theater with Shepard in residence at the Signature, and Mednick's Joe And Betty, which was produced twice on Theater Row in New York. In 1997, Diehl reprised his role in Action at the Public Theater, and in 2005 he worked once again with Padua Playwrights, appearing in two plays in Mednick's Gary Trilogy. Among others, his theater credits include Life of Mine, (with Holly Hunter) at the Mark Taper Forum, Samuel Beckett's Endgame and Happy Days, one of three plays which Diehl directed. He has appeared in more than 140 films, including Joysticks (1983), Angel (1984), City Limits (1984), Madhouse (1990), The Dark Side of the Moon (1990), Kickboxer 2 (1991), Mikey (1992), Mo' Money (1992), Gettysburg (1993), The Client (1994), Stargate (1994), The New Age (1994), Mind Ripper (1995), A Time to Kill (1996), Pearl Harbor (2001), and Road to Nowhere (2010). He played G. Gordon Liddy in Oliver Stone's Nixon (1995), the mercenary Cooper in Jurassic Park III (2001), and in recurring roles on The Shield, Friday Night Lights, The West Wing and The John Larroquette Show. In 2000, he appeared in Fail Safe, which aired live on television. Between 2002 and 2004, he portrayed General Motors' Harley Earl in a series of television commercials for Buick. The commercials were directed by Tony Scott, who had previously directed films including Top Gun and Crimson Tide. In 2004, Wim Wenders cast Diehl as the male lead in Land of Plenty, a film about post 9/11 American life.