I have the showa PSS metering units. The metering units were in need of a clean.
I was told that they should just be replaced, one price I got was around 20 quid[pounds] each and there are in excess of 25 of them.
I wondered if any one had cleaned them successfuly. I stripped them and pumped filtered petrol through the filter backwards. It took several goes for a resonable stream to flow through the filter in the correct direction. But the filter is probably still full of the crud. I was tempted to buy one, so I could cut the filter open on one of my old ones and see what it looks like.