So I decided to find out why Nuatilus delays to syntax highlight when I open ChronosManager I open my activity monitor to be amazed by the fact that pharo was consuming 30% of one of my cores.
At the time I thought it was my fault because when my GUI steps I load from a png a form that I attack to a Morph. So I optomised that part loading all the pngs before hand , creating all the forms and during steping point only to the correct form.