What’s the best way to replace connectors? Solder or re-pin? And if it’s the latter, is there a trick to removing the pins? I can’t seem to get these out (but the socket is not OEM)
I have always preferred to re-pin them myself. I have replaced a lot of connectors over the years so it made sense to purchase the appropriate pin removal tools.
The one on the left above is what you would use to remove the pins in the particular connector you have. You can also get away with using a couple of small flat bladed precision screwdrivers or a couple of sewing needles. I have used both of those successfully in the past before I purchased the specific tools.
Corrosion is an issue with some of the connectors in these vehicles. If that is the problem you are facing, you can buy a blank housing and new pins that already have the wires crimped on. That way, you do not have to remove any pins. You just insert the pins in the housing and solder the wires to the harness.
with that tool, or a sewing needle, do you remove the pins from the bottom? like with a 2-prong “corkscrew” Is the goal to break the air seal of the gasket each pin in place?
Typically their are small protrusions that lock the pin in place. The tool presses them flat.
Ed
Can confirm that the pin removal tool is worth it. I want to say I got mine at ECStuning.
I had to replace a broken fuel injector connector. 12 hours of labor for a $10 part. But at least my labor was free 
edit: youtube link for VW/Audi pin removal tool
Anyone have any suggestions for where to buy VAG quality connectors and rubber grommets? I see the smaller connectors on ECS but no rubber grommets. Anything else I’ve been able to find seems to be from China.