The guy in the red car who looked like Mulder was Steve Kiziak, who was David's double on the series. This episode was written by Vince Gilligan who wrote Bad Blood which you enjoyed so much. This episode was shot before the previous two and at the time both David and Gillian were finishing shooting films, so they were not featured quite as much as normal. That's also why it's noticeable that David had his new, shorter haircut!