One thing not generally known is, stock evaporator valves have (or had) a fine bronze screen to catch rubber hose and dryer particles before they jam up the compressor. It is conical, about 1" long, in the side port of the valve. It simply floats in there- hook it out with a scribe and soak in some sort of solvent that dissolves rubber.
On the ones I've seen, they are packed solid with debris and will certainly reduce freon flow. The little screen is not soldered- aggressive cleaning will destroy it and replacement valves do not include this screen anymore. Some AC mechanics intentionally leave it out to slightly increase freon flow for more cooling.
Loosen the valve with TWO wrenches- backing up the assembly with one wrench while using the second to undo the nut. I fully realize access is limited, but NOT doing this will twist the line off your evaporator, and they can't be repaired. So out comes the dash for access to change evaporator$. Several 'pro mechanics' have learned this expensive lesson on Pantera AC.