I had this problem for a good year and a half, when stopped at lights and when it warm it juddered like a motherf*cker, like a violent judder. I left it for a good while because it was only every now and again.
About 2 months back I had a some work done on it, I had a coolant leak from my water pump so got that replaced and I had a leak from my intercooler pipes which I had sealed up.
Since this work the violent judder has completely gone, and ive done a trip around Scotland in it which took about 800 miles along with the rest of my usual mileage so its been well ran in since and not had it come back once. Not sure if you have the same problems, but its another place to look if youve checked out the timings etc?