smoke out exauhst and limp mode engaged

Hi all was wondering if anyone had any ideas about this situation i am in .

I have a 2012 Mk11 1.6td Octavia  which over the period of a week started getting the heater plug light come on the dash as i was driving flashing so a friend at work has the car doctor diagnostics tool so he plugged it in and everytime it came up EGR valve and eventually the engine management  light came as well and went into limp mode but i was still able to scoot along the road to my work around 50 mph most of the time the lights would go out after stopping and turning on and off the car .

So i organised a friend to fit a brand new EGR valve who by the way is a mechanic and he done this he said he took it for a drive and it was fine but next morning it was getting picked up for to go for a MOT the guy got about a mile down the road then car went into limp mode and would not go over 10 miles an hour and smoke started belching  out of exuahst but my mechanic friend is lost as to what this can be as he has had it plugged into diagnostics and there is nothing on it saying its doing this has anyone had similar  happen to them after changing egr valve or does it have to be mapped into system again seeing as its new or any ideas Thanks