quite sure the TRD is 2.25".... sorry for bringing this thread back from the dead i did a search but i was jsut wondering if u get a full exhasut system ex Headers Spipe Midpipe TRD axel back is it still restricted and no gains? or Changing the midpipe making it a catback not restrict it at all? im wondering casue i want to get a spipe and either get a midpipe ...or change my exhaust completly and get a catback... i want power and good sound so if the TRD axel back restircts it even if u change the midpipe..i rather buy a new exhasut system