I had the same symptom after I replaced my old failed alternator. At the same time, my positive battery cable was getting rather hot near its connection to the battery post. I replaced the cable and also removed and cleaned all contacts at the Mega fuses and the flickering was gone. Later, I also replaced the negative battery cable although it seemed fine (was not getting hot).

 

I checked the voltage at the battery, 13.86 jumped to 14.10 when flooring it, so it appears the regulator is regulating, as before I was getting 15.5+ at idle, i just have to figure out the flickering now and the restricted performance warning that has appeared

 

Which ones are the Mega fuses? My battery cable appear to be in excellent condition, no corrosion at either end and they dont get hot, but thanks for the tip. I will clean and re-connect the positive

 

Three large fuses in a black box in front of the spare wheel. As for the battery cables, they can look nice and shiny but they tend to develop, over time, resistance in the crimps to their terminals. Anyhow, try first with cleaning and tightening properly the Mega fuses.

 

are you talking about the fuse box next to the battery?