6xdad

my daughters 05 legacy is doing something similar, it is an auto, but when starting out or accelarating after coasting, the engine revs and then the transmission engages. It is like having the clutch pedal depressed on a manual and letting it out, it will grab, but not quickly and has to be over 2k rpm. Is there a vaccum line that could be malfunctioning? Or does it sound like something worse/