Ok, I think it might be able to block ports, maybe, You'll have to see since you have this program.
1. Set up a Schedule rule. Set a time frame of when you think you want to block any access for the PPStream ports. Tools/Schedule.
2. Got to Avanced/Access Control. Enable the check mark. Give a Policy name, can be anything. Next.
3. There should be a drop down menu, might say ALWAYS. Select the drop down and the Schedule name should appear that you set up. Select this name. Next.
4. On the next screen, there should be 2 or 3 selectable options, IP, MAC and Other Machines. You'll need to see which one works for you best. I would test Mac or IP first. Add the IP or Mac to the policy by selecting the Drop down for the PC you want to test, then ADD. Next.
5. Select the method for filtering, Select Block Some Access. Also select Apply Advanced Port Filters. Next.
6. Add Port Filters Rules screen is where you'll need to enter in the ports that your trying to block PPS from accessing. I would leave Destination IP Start and End at default. Select either TCP or UDP, this will enable the Dest Port Start and End boxes. You'll need to figure out if PPS uses TCP or UDP. Input the first port that you want to block, enter in the one port number in both Dest Port Start and Dest Port End.
7. Save the setting or apply it. Reboot the router and test to see if the port is blocked or of PPStream is failing to connect.
You'll probably have to set of multiple rules maybe for each port that needs to block the PPS ports. You should be able to set up the Dest IP Start and End Range just like you did in QoS so those PC that your trying to block, will be included in the range for this rule.
Let us know if this helps. The process is using a different DIR series router and I don't have the 655 online at the moment. Please let me know if these steps are not correct.