Catchy title, just a couple of tips. I had purchased some filament from a new vendor on Amazon. After several failed prints (filament grinding), I pulled the filament back into the spool and noticed a considerable resistance from the filament. After getting it out of the Teflon tube, I measured the diameter and found that the filament was oblong 1.75 mm on one orientation, 1.9 mm on the 90 degree orientation. It's discouraging to see out of spec filament. It has been said may times on this website, buy filament from a quality vendor. Anytime you change the hot-end, you should run the PID wizard so as to fine tune the temperature control firmware / software. And probably should revisit "leveling the bed", especially if the nozzle is different from the old hot-end. Procedure can be found at the top of the Troubleshooting forum.