ISG Rest services overhead issues

Hello, does any one has performance issues with the ISG REST services calls (overhead)? our calls taking long time, from logs/detail show in table fnd_log_messages, most of the time consume before the actual webservice is excused, for example, the actual services execution take less than 1 second, but before and after the execution, there are lot of other stuff consume most of the time. if any one has the issues, can you please let me know how did you get it fixed? If there is any patch that can fix the overhead? we are in the latest EBS patch level.