2010 Fusion Decelerates/Loses Power - Intermittent Fault

My 2010 Ford Fusion 1.6 Auto - 16,000 on clock - is currently in the Ford garage (having been transferred from our local garage which lacks diagnostic equipment).  A couple of days ago it started to rev hard on starting.  As I pulled into traffic, the power just drained away and the car decelerated to just 7mph.  A single ( ! ) warning light came up on the dash.  I managed to pull out of the traffic and crawled the mile or so to the local garage.  As  soon as the engine was turned off and then on again, the fault disappeared.  Good old Google shows that this is a known problem with newer Focuses and Fiestas, and a wider search reveals that this is the most common problem reported by Fusion owners in the US.     The Ford garage has confirmed that this is a common problem with newer Focuses/Fiestas, but Ford have not accepted that it also occurs in Fusions and therefore the adaptation I'm told it will need to remedy the problem is not covered by the Ford Warranty.   Any one else had this problem with their Fusion? Has it been resolved?  If so, how?   Cheers!