When my printer arrived the PTFE tubes were bent in a strange way, which led to problems when feeding the filament for some fast prints.
I couldn't find a solution to my problem with a small footprint, so I created one. Simply feed the tube through the guide and slide it on the output. There should be no additional strain on the PTFE output. Please note that the guide is not symmetrical, the side where you press to feed the filament is slightly lower than the other side.