i3 here with a J-Head Mk v. Lots of warping of larger parts (Wades extruder, or the X-carriage) until:

Kapton, 105 degrees. Make sure the whole bed has heated evenly so leave for 15 mins after it has reached temp.
ABS at 235 degrees
No fans, draughts, door closed!
ABS paste on the kapton. Until I applied the paste I failed.

Now it's all working!

I still get minor layers peeling from each other occasionally.