I had the same thing happen to my RRV. It turned out to be the injector hose had split between the intercooler and the turbo. It happened at the lights when I went to pull away, lost all power and had plumes of smoke billowing out of the back of my RR. The pipe costs about £80 + labour to fit. Very easy fix if that's what's gone on yours. I had a couple of goes at getting it fitted as it is apparently very hard to get the hose fitted and jubilee clips tightened.
Good luck!
Matt.