Powerwasher Help

I am getting low pressure with my Simpson Power Washer, I replaced the pump with an OEM, Carberatuer, hose, changed oil, and spark plug. It starts in one pull but seems like it's not getting enough RPM when I pull the trigger. I've manually move the governor arm when it's on and it doesn't increase the pressure, just idles higher. I'm about to give up. It has the same symptoms throughout all my efforts.