Here's an example of how I clear the restriction in the Carrier (or Trane etc) RTU's that have the multiple parallel path piston orifices. (I have a habit of calling them "accurators" in the videos because that is what Carrier calls their piston metering devices).

Typically HVAC technicians either replace the entire metering device header assembly (which is a lot of work) or they replace the entire coil.
So far I have had some luck with clearing these restrictions.

What I did here was cut the piping going in and out to isolate the section I am going to clear and I heat the copper around each piston until it is near cherry red then I blast it with nitrogen.

The debris are known to be caused from some sort of wax build up from the oil etc.
Heating the pistons seems to melt the wax so it can be cleared out.

I also used my Spinning Swage set to put the copper piping back together with a factory look.