Below you can the measuring points for the oil pressures inside the transmission.



At the top at A you measure the working pressure, that is the pressure from the pump. Use a pressure gauge up to 25 bar. Measuring is done by disconnecting the vacuum line at the modulator and running the engine up to 1000 rpm with the transmission in D. Use both parking brake and normal brake to stop the car. The pressure should be 12.5 bar plusminus 1 bar.

At R you can measure governor pressure, that is the pressure which pmckechnie is talking about. Use a pressure gauge up to 10 bar. At 30 km/h the pressure should be 1.2 bar; at 90 km/h it should be 2.8 bar. There is of course a problem, as that speed is not obtainable at the moment. But the pressure at 30 km/h should give you an indication.

At M you can measure the modulation pressure. Use a pressure gauge up to 10 bar. Disconnect the vacuum line and drive in D at 50 km/h. The pressure should be 2.9 bar.

I'm thinking that the pump isn't pumping out its full working pressure, that affects the other pressures too, as other pressures are derived from the working pressure.

All this info is from the German FSM.

Here is a close-up of the measuring points M and R:



To the below-right of #60 is M. Below #12 is R.

If the car isn't running, you can remove a screw to get the fitting. Oil will not stream out. You need a pressure line too, long enough so that it can be fed into the car interior

There are two teflon rings too, below one old one:



and some more O rings:



Did you torque the bolts of the oil pump to 20 Nm?