According to RabbitTDGuy from VWDiesel:
ALH and AHU pistons are the same. They are quite a bit stronger and less "crack prone" compared to the 1z TDI pistons which are single piece "cast" units.
ALH/AHU units are beefier in their construction, are made from a different alloy and also have brass...
You need a BEEFY slide hammer. I used the metalnerd one and it didn’t budge them one bit. I received a slide hammer from DBW LLC which appeared to be custom built for the application and it knocked them out in a couple pulls. The slide weight was easily 3x the weight of the metalnerd one.
If you are doing the top seals, you can read injection quantity with basically any scanner. If you wish to do the pump timing (different procedure) you will need to buy or rent the VCDS cable and download and run their software.
Got the AC recharged again yesterday... the system held a charge for roughly 1 year. The tech said that they needed to flush it 3 times to get all the "crud" out, and there was more "crud" than the last time I got it recharged. I am going to guess that the compressor is on its way out. After 24...
Bubbles in the fuel line indicate some sort of loose connection or air entering the fuel system. This could be a chafed hose, residual air in the fuel filter, etc. The thermostatic coupling atop the fuel filter can be a source of leaks.
Either way, sounds like you found your issue.