hi all, when i let off the gas on my 01 V70 T5 the engine will return to around 1500 rpm and it shakes( sometimes violently) as if i was in to high a gear for the road speed!! as this isn't the case i wonder if anyone on here has ever had this fault before as its driving me insane as just cant figure out whats going on

no warning lights, no codes and can't see anything out of place/broken

help anyone!!??