Polaris Booster pump PB4-60

Tested Polaris PB4-60 booster with Polaris test stick. I only have 16psi at the gauge and cleaner is moving slow. Is there a different pump I need or a way to boost the pressure? I currently have the blue disk on the in wall fitting. Tried the red but pressure went down to 11psi. Using Polaris 280 cleaner that’s pretty new. 
Thanks,

Don