I have bougt the expansion yesterday evening and did a flight from eham-kjfk without any problems but then on the way back i tried the time compression function up till 4x timecompression there are no problems but then is selected the 8x timecompression and the plane starts turning and it can't keep the flight path and the instruments says its turning without turning the plane can anyone help me please it'sreally anoying and it cant keep the altitude either when at 8x timecompression

This is an issue they are working on. Some people have it (including me,) and other people don't. 

see http://forum.avsim.net/topic/446758-problems-with-time-compression-8x/