Has any of the components been replaced from the original installation? Do you have the same compressor, TXV, etc?

Second point... With the exception of one post all of the data you are suppying to us is temperatures. You need both pressure and temperature to find problems.

What is the suction pressure and discharge pressure (don't call that the exhaust pressure, you will only confuse others).

What is the suction temperature and discharge temperature? Both of these you can find with a thermometer at the compressor service valves. About 6 inches away from the valves should be fine.

Next question: What kind of condenser do you have? Air-cooled I suspect. Does it have any dirt in it? Look at both sides of the condenser coil. Sometimes you have to blow them out with compressed air.

Next question: Are there any regulating valves in the suction line between the cold plates and the compressore suction service valve?

How was the system charged with MP66? If you charged it with gas, you will have some problems. That is what Peter was describing I believe.

What is the liquid line temperature after the receiver, or condenser?