While doing hardline on my son 2010 Golf air ride installation I damaged one of PTC cartridges on the AirLift V2 manifold
You can't just remove it to try and fix it the removal process destroys the cartridge. Replacement for the AirLift 1/4" manifold is a Parker #PMTCE-4, 3/8" PMTCE-6 cost about $6.50 purchased mine online. Was told by OnlyChargedDubs that BagRiders may be able to help with these. I tried to order one from OnlyChargedDubs site but their in the UK and site won't accept your request because the shipping cost is greater than the cost of the part.
Here is a video on how to remove it:
Here is a video on how to install it: