[LMP]

INdeed, you probably had a backfire, a minor event, for unknown reason (to be investigated later if it perdures), but it obviously blew a vacuum line out, whick inhibits the brake booster and provides poor idle; you will probably notice none of the heater/AC control will work to direct air where you would want it; cruise control will also be inoperative because it works from vacuum. THe main vacuum hose is between the intake manifold and power brake booster. Check for this.