Mine has the PTFE tubes inside the heat tube. I've replaced it many times over the few months I've been printing. I bought some 3mm twist drills that I use to ream out the tube and nozzle, as well. The PTFE is a pretty snug fit and it is sometimes difficult to get the length of the piece just right. Too short and it develops a blockage and too long, and it twists and constricts the filament.
I've looked a new dual extruder (J-style $140 in single qty on Alibaba) but I'm not confident in my ability to deal with the possible changes to firmware to regulate the servo.

A few weeks ago, my printer really started acting up. I have to run the extruder at 240 to 245 to get PLA to print properly - I used to use 190 to 200. Also, I used to have luck with a small fan to reduce curling on my overhangs, but now the fan just cools the nozzle enough to screw up the feed. Maybe my thermister is leaving the room...

I haven't used my left extruder for months. I should try it just to see if the printing temperature is closer to normal. Haven't ever got PVA to work, so I just have the nozzle off so it doesn't snag the print. I think my plate may be warped slightly (up in the middle). I've got some ABS and HPS, but the printer is in the house and I don't think the boss would appreciate the odors. I haven't gotten nylon to work either.