could be u coil pack thats gone south for the summer as this happened on my lcr , a few months back , are the symptoms :- drive in low revs ok accerlerate and the juddering is quite fiercely felt thru the steering wheel and obvious loss of power then will it be ok further into the rev range , I had the AA out to mine courtesy of seat assistance .
We test drove it and changed the coil over each 500 yds eg but he could find which one had gone , in the end seat replaced all coils 4 me .
so I think it is ur coil packs that have gone .....