I have just upgraded my old Makerbot Replicator 1 (dual). I am so impressed with the Bondtech extruder, made such a big difference. Printing flex filament at 4000mm/min is a breeze. Now I need to find the optimal settings in the slicer and also try faster speeds check out (and DL if you want) my initial print tests here https://www.thingiverse.com/thing:3253619