[usmc grunt]

When I am decelerating (as when letting off the gas pedal while behind a slower driver) and then press lightly on the accelerator to resume something weird happens. The truck slows down faster than when just letting off the gas. It feels like their is an increased drag or resistance. If I apply just slightly more pressure everything seems normal. Not knowing too much about vacuum systems, I am guessing that maybe that is my issue. However, I have not had any engine light warnings and I know the Tundra has sensors and warning lights for every imaginable issue. Should I be concerned or is this normal? Any help is greatly appreciated.