Makerfarm Prusa i3v 8" flex extruder advice needed please...

I want to run ninja-flex and the existing extruder is not working well. The filament keeps jamming up at the hobbed bolt. Is there an extruder that works well with ninja-flex?
Saw several on Thingyverse but don't know which one to get.

Thank you
Bill

what size filament are you using? If it's 1.75mm, adding a filament guide tube to the extruder body might help, like I did here - http://3dprintboard.com/showthread.p...ll=1#post26647

I have 3mm.