Hi there,
The only thing I did to the TAZ3 was replace the PEI sheet on the glass bed and added a filament cooling fan. The drylin bearings need replacing but haven’t bought any yet. The under extrusion problem seemed to have gone away. Apparently the filament diameter setting was set to 3mm. I changed it to 2.85mm and it seems to print just fine. As I previously mentioned, this is a hobby printer and I haven’t had much time to futz with it. I use my TAZ6 and Prusa’s all the time.
Not sure if the TAZ2.1 is worth $400. For that money you can get yourself a Prusa mini. I have one and it is quite nimble. I’m a fan of both Prusa’s.
-Mike
Here’s a link you might find useful.