Check your air pressure. If still pulling/drifting try swapping the right side tires
only front-to-back and drive again.
Other suspects are:
Two right-hand tires with similarly offset belts
FWD models experiencing torque steer (if the pull only occurs under acceleration)
AWD models with bad rear drive (ditto)
Worn and/or notchy front suspension joints
Front suspension bent to the point that the S.A.I. is way off
LF caster greater than RF
Rear toe off so far as to cause dog-walking or forklift steering
Power control valve in rack defective (center wheel, start engine. if the wheel jumped slightly to one side this is a problem)
Passenger needs to go on diet (but you didn't get that from me - if you tell them that you're on your own!
)