You have to adjust the Vref with the steppers' potentiometers at the mainboard.

Search for "4040 extrusion endcap" at Printables for example, plenty of models to find.

The reason is that the firmware and profile have 220x220mm bedsize set, but the physical dimensions are actually 230x230mm. Since the 0,0 origin is in the left bottom corner, you end up with a model that's off-center 10mm to the left and bottom. You can try and just change the bedsize in your Slicer to 230x230mm.

Oh wow - thanks for the kind words! :)

Yes, basically it's the head's PCB. The extruder gear is slightly different between those two heads (K2Neo is single gear, K2Pro is dual gear), but the reason you can't use the K2Neo's head at the K2Pro for example is the PCB, correct.

Welcome! :)

It's noticeable that you have more layers applied at the right hand side, so you might wanna tram your x-gantry.
Besides, make sure to avoid any wrinkles and bubbles when applying Kapton tape.. ;)

The RPi is connected to the Vyper with a USB cable.
The RPi then has to access your local network and then you can access the Mainsail UI (or Fluidd or OctoPrint, whatever the guy installed) thru your webbrowser by accessing the IP of the RPi and/or by typing mainsail.local.
Try using a LAN cable instead of a WiFi connection. Then check your router to see which IP address it gave the RPi.
If that doesn't work, contact the guy and ask him if he still has the files for the Vyper, most importantly the file called printer.cfg. That one contains all the machine specific settings. If he has it and sends it to you, you can set up a new installation for your RPi using (e.g.) the "Raspberry Pi Imager" and install the MainsailOS with your WiFi settings etc. I'd take a new mSD card for that, so that you still have the original one that came with it. Then boot up your RPi and once you can access the Mainsail UI, upload the printer.cfg for your Vyper.

Iirc it's a JST PH 2.0 type of connector. You can cut off the original one and solder it to the new fan if you don't have or don't want to get the crimping tools.

Yes you can. You'll also find some infos here.

Only the K2 Pro, Plus and Max are using the exact same head - it's different than the head of the regular K2 and K2 Neo.

If it's not coming out the threads between either the nozzle and the block at the bottom or the heatbreak and the block at the top (which would indicate a wrong assembly), then it's most likely filament that's being caught and crawled up between the silicone sock and the block.

Heat up the hotend to ~120°C, then *turn off the machine*.
Then carefully take off the silicone sock and clean the parts by removing all that squished filament.
Reapply the sock and print sth. Once done, take off the sock again and inspect the top and the bottom to see if filament squishes out at the abovementioned threads. If that's *not* the case, everything is fine and you just need to clean your hotend more often.

Since the K2 Neo is running Marlin, you can't just change a setting in the fw w/o recompiling it - so to avoid all that hassle, you wanna try and go with the M900 K<factor> command instead, as already mentioned by u/PoisonKappa. Read this description of the command, should be helpful: https://marlinfw.org/docs/gcode/M900.html

Just fyi, this is the according setting in the fw:
``` /** * Linear Pressure Control v1.5 * * Assumption: advance [steps] = k * (delta velocity [steps/s]) * K=0 means advance disabled. * * NOTE: K values for LIN_ADVANCE 1.5 differ from earlier versions! * * Set K around 0.22 for 3mm PLA Direct Drive with ~6.5cm between the drive gear and heatbreak. * Larger K values will be needed for flexible filament and greater distances. * If this algorithm produces a higher speed offset than the extruder can handle (compared to E jerk) * print acceleration will be reduced during the affected moves to keep within the limit. * * See https://marlinfw.org/docs/features/lin_advance.html for full instructions. */

#if ENABLED(DISTINCT_E_FACTORS) #define ADVANCE_K { 0.02 } // (mm) Compression length per 1mm/s extruder speed, per extruder #else #define ADVANCE_K 0.06 // (mm) Compression length applying to all extruders #endif //#define ADVANCE_K_EXTRA // Add a second linear advance constant, configurable with M900 L. //#define LA_DEBUG // Print debug information to serial during operation. Disable for production use. #define ALLOW_LOW_EJERK // Allow a DEFAULT_EJERK value of <10. Recommended for direct drive hotends. //#define EXPERIMENTAL_I2S_LA // Allow I2S_STEPPER_STREAM to be used with LA. Performance degrades as the LA step rate reaches ~20kHz.

```

Here you find the sources: https://github.com/ANYCUBIC-3D/Kobra2_Neo/tree/master
And if you really want to change settings in the fw and therefore have to compile it, read along this reddit post: https://www.reddit.com/r/anycubic/comments/y2waxu/tutorial_how_to_build_anycubic_marlin_source_code/ 

Imho the only necessary upgrade is a different fan duct. Well, and Klipper.. ;)

Check the PTFE inliner at the heatbreak, it might be clogged, deformed or even molten.
Check the nozzle as well, it might be time for a new one.
Also check your retraction settings - if you're using AC's profile with 6mm, then it's way too much for the direct drive of the Neo.
Check https://1coderookie.github.io/KobraGoNeoInsights/ for more info and tips.

If you apply so much force to the edge of the build plate (= big lever) that you already twist the bedgantry, as seems to be the case in your video, then it can be considered normal, yes.

Unlike a CNC machine, a 3D printer doesn't have to deal with a lot of vertical forces, so if all the screws are tight and the SG15 bearings are well positioned with the eccentric nuts, then you're good to go.

As a general rule, try to avoid removing the PEI plate - just wait and let the bed cool down completely, then the prints will pop right off the PEI plate.

So you are talking about the motor's pulley for the belt then?
If so: clean the dust and check the belt tension, you're most likely running them a bit too tight and face increased wear&tear.

Thanks for recommending the KGNI infosite - actually there's one about OP's Kobra2 as well tho, so that should be even more helpful for him :)

You could start reading along here: https://1coderookie.github.io/Kobra2Insights/ -> that site is specifically made for the K2. Mind the chapter "Calibration".

So all those users who claimed to have updated the initial fw to this version must have been lying - alright, well, whatever..

Depends on when you bought it..

That dust is caused by wear&tear - wipe it off, add some lube to the rail and adjust the wheels' position.
Those wheels are so called "SG15" bearings. AC does sell them, but it seems they don't ship them to the US right now: https://store.anycubic.com/collections/accessories-for-fdm-series/products/sg15-pulley
You can look around at other shops like ebay, Amazon, AliEx tho, you'll find them.
See this chapter and the subsections for more info - hope it helps..