My C85/1 machine is no longer developing full brew head pressure. I have a gauge that screws onto the filter holder. Normally I could get as high as ~13 bar and set the OPV for 9 bar. I measured the pressure at about 4 bar and have done the following:

1. Adjusted the OPV
2. Removed and cleaned the OPV
3. Removed and cleaned the UKLA NH 260
4. Replaced the pump with a Fluid-o-Tech 1106 with the B2E relief valve factory preset at 10 bar.
5. With the OPV fully screwed in, pressure is still about 4 bar.

What can I do next?

check for scale build up in your water path like the hx injector on the bottom of the boiler and posiably check the gicleur in the head as well for buildup in the screen,

An item I inadvertently left out of my original post was about my water supply line pressure. The incoming water line pressure at our house is 70 psig. I do not have a line pressure gauge at the machine so I don't know what the actual pressure at the machine was after the house piping and the 3/8" tubing connecting to the machine. I have read recommendations that 30 psig is desired at the machine. I installed a 30 psig pressure regulator and think this is when all of my problems started. I am collecting the fittings to put a gauge at the machine. Since 30 psig is the maximum recommended by Fluid-o-Tech for their pump, I don't really want to take the regulator out of the line until I know what the pressure is.