So you just get your printer and you have that urge to trick it out with all the tweaks and upgrades you can find. And guess what, you can print most of them right off the web. What better way to show your new machine some love?
So now you spy a method by which you can guarantee smooth movement of filament through the PTFE tube. It seems like an elegant solution so why not?
Then you go to print this elegant solution but the one question that hasn’t been asked; if this was such an obvious solution and there is and example of it nearby the printhead for the wires, why would the manufacture overlook such an obvious upgrade? Or more importantly, why wouldn’t they offer it in their store? Or perhaps even a download from their site?
If this story feels like it’s familiar, trust me, some of us have gone this path before. 
Our esteemed community member and respected moderator @jonraymond is far too polite here. I am not. So I will give you the skinny on PTFE tube guides.
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If they were needed and if they actually worked, Bambu would have either included them as part of the original design or the PTFE chain upgrade or simply made them available for sale. The fact that they did not do so should be a red flag that they know something.
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They simply do not work, they are a liability, not an asset. Ask me how I know. 
This collection of PTFE tubes were various versions printed in everything from PLA, PETG, ASA, ABS and even PC. I ran experiments for the first four months of owning my P1 and experienced a lot of issues. Then one day when servicing the PTFE tube, I forgot to replace the PTFE guide. Low and behold, my nagging problems mysteriously stopped. I replaced the PTFE guide and they came back. When I say problems, I mean ringing, layer lines and yes, my tool head cover being knocked off.
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Last comment and warning to all newbies.
If it’s on the web, don’t assume the person who put it there knew what they were doing—or even tested it. Sure, they might’ve posted a pretty picture, but MakerWorld incentivizes volume, not proven quality. And if it has a Bambu logo on it? Double your skepticism. That’s the oldest trick in the book to bait newbies—because who wouldn’t want to deck out their shiny new printer with some Bambu-branded bling?
It’s like the guy who buys a new car and immediately slaps on aftermarket floor mats with the brand’s logo to impress his girlfriend. Be honest, we’ve all done it! 
Linking to the MakerWorld profile directly so other’s can see the report made above. PTFE Tube Guide by 3DTechBase - MakerWorld
Note what this uploader said in the profile:
This reference to PLA is what I’d call a smoking gun. Anyone who’s ever put a PLA part in a chamber that gets even mildly warm (30°C or above) knows it warps. Anyone who’s used PLA for a mechanical moving part also knows it’s way too fragile material to stand up to repeated shock, vibration and flexing. So why did this uploader list PLA? Simple—the more filaments he claims will work, the more people he can trick into downloading his model. Because hey, he wouldn’t lie… right? 
And BTW: If one were to use a material for a PTFE guide. The best that I tested was ABS and PC. CF would probably work well but would be far too abrasive and eventually ruing the tool head coupling. If I weren’t so cheap to waste money on a Nylon filament spool just for this experiment, I’d wager that would be the ideal material between strength, low friction, temperature resistance and shock resistance. But I am not spending $35 on a spool of nylon for my P1 that can barely reach the temps needed. For that, I’d wait till I get a Qidi 4 Plus, not a Bambu Printer.
