Chris,
The problem you described is a little vague. Maybe you can answer a few questions so I can have some data to help troubleshoot your machine.
Is this a hot pressure washer or cold water unit? What kind of unloader are you running?
You may have an unloader problem. (Sometimes K-7 unladers and others will partially hang up in bypass) this would show symptoms similar to what you described. If you pinch off the bypass line WITH GUN OPEN ONLY the pressure will increase if you are bypasing water.
Call me if I can be of assistance.