Ford Fiesta 1.4tdci-she almost died on me today..any ideas?

[Craig-o]

Driving to work today (got called in on my day off ) and the car was driving fine all the way until suddenly just out of the blue the power dropped right off for about 5 seconds and with my foot planted the car almost stalled.....smoke piled out of the back for those 5 seconds and then it just picked back up again and carried on as normal

Any ideas what could have caused this? Plenty of fuel in it....just seemed to drop off boost but then totally lose power for a few seconds then carry on as normal.....no warning lights came on the dash or anything.

Cheers, Craig