Looking for some insight on repairing 2 issues with my Livia 90. First issue, air in the line, and losing pressure. This was remedied by blowing off steam to purge the line. Has not been much of an issue but still, persists

Second issue, and why I've torn it apart. VERY weak pressure at the grouphead. With no portafilter even in place it just drissels out. Takes a very long time to pull a shot. I was thinking needed descaling, and tried that, with the blank, and the drain leaks a bit while the shot is pulling and pressure releases when stopping brew. I thought 3-way valve so started there. Electronically, its fine, and the valve itself is crystal clear, no calcium at all. I am soaking all valve components now just in case. Also looked into the other solenoid, back-left of the machine, also clean. Also checked all lines going into the HX, clear, no blockage.

At this point I'm stumped, nothing seems wrong but it struggles to pull shots. Thanks!

Try disconnecting the line between the pump outlet and the OPV group and run a bit, to get any air within the pump out.
It may just be air bound.

Didn't appear to have any air. Same issue persists. Could it be the 3 way valve sticking?

Possibly line or port partial pluggage leading to or from the 3way Valve/
Real possibility after descaling, especially if lots of solids need to be removed.

I haven't found any solids or any hint of contamination. It's clean as a whistle in all the lines. Still very weak.

Possible bad pump, or weak spring in the over pressure valve assembly, in the line going to the drain.