What style/design of direct drive extruders do individuals prefer these days? I cannot seem to break 85-100 mm/s without having my filament grind, or motor skip steps (regardless of changing the temp). Current set-up is here - http://www.thingiverse.com/thing:24992 using a PG35L gear motor and Budda hot-end (Video of my set-up https://www.youtube.com/watch?v=VkFEpesc7pc)
You might want to look at the heater. As you print faster, you must extrude faster, requiring more heat energy. It is possible that your head temperature is dropping, causing the back pressure to be higher. Put a temperature probe on the hot end to monitor it or bump your temp up before you start.
I have a RichRap geared extruder and a bowden E3D hotend. I can print PLA at 0.3mm layers at 200 mm/s without problem. Maybe could even go faster, haven’t tried it.
@Shachar_Weis how many watts has your hotend?
I have monitored my temp during a print cycle and found it did not vary more then +/- 1.5 deg c from set temp. I have tried increasing the set temp but found only minimal improvements after setting the temp to the high side of print temp (220 for PLA, 240 for ABS).