traffic passing through my firewall is giving me high ping time (5ms-10ms), and this is causing problems to us since our application requires time around 2ms, can someone please advice, kindly to note that all PCs and Servers are in the same location, no wan links and far nodes to reach.
Really the correct way to deal with this issue is either in your application design or your network design. I wouldn't feel confident in guaranteeing latency lower than 5ms at all times through a firewall, particularly a relatively old device such as an SSG or Netscreen. In addition, an application designed to work correctly only with a latency of 2ms is pretty seriously flawed.
I would advise either redesigning how this application connects to whatever it needs to connect to (i.e. bypass the firewall and either route or switch directly), or getting the application modified so it can deal with latency above 2ms. I don't think you'll be able to resolve this permanently by changing anything on the firewall.