After a while my retractions settings were not looking great. looking at slic3r a bi more closely, i realised the settings for retraction speed was in mm/s not mm/min, therefore the setting of 30 was causing the stepper to screetch!
i reduced this down to 4mm/s and 4mm retraction which was painfully slow, so a quick q on REPREP IRC channel brought Dreamscape74 suggesting their settings.

Now retraction is set at 14mm/s and 2mm retraction length.

Now onto the brige test…