EDIT to include my post below. Again, use at your own risk! This was disabled by Prusa to fix USB issues, I don't see why us sdcard users should suffer for it until they figure out a fix.
Brigandier wrote: ↑Sat Feb 10, 2018 1:28 amTook the plunge, uncommented the LIN_ADVANCE line in the latest (3.1.1) release. Already seeing massive improvements on my PETG.
Now, I don't know what Prusa's opinion is of people posting customized firmware so if this is violating anything please let me know, but if you guys are interested please find it attached. This is the firmware from the MK3 branch on Github, with the only adjustment being line 321 in Configuration_adv.h to uncomment #define LIN_ADVANCE. Best I can tell, all LIN_ADVANCE references elsewhere do an "ifdef" to check if this is defined or not.
DISCLAIMER: I am NOT a Prusa employee or necessarily even that great of a programmer. You are using this at your own risk and on the premise that it is working okay for just me on a couple prints thus far. If the details in this thread are accurate, you do not want to use this if you do any type of printing over USB. This is for sdcard users only!