Engine knocking?
 

Listen carefully

https://youtu.be/OxmU9ZLTsx8

Hear it? Slight knocking at around 1,000rpm? That wasn't there before. Any possibilities?

And if anyone jumps on the IMS band wagon I'm going to slap them. Not everything is down to that.

Thanks!

Hard to tell from inside the cabin but I would guess the lifters. Mine went soft with only 39k and were making noises. It could be something else though and I'd remove the engine cover to get a better look

It depends if you want speculation or diagnosis :-).
Get the car up on a lift. Use an engine ear(electronic stethoscope ) to pinpoint the exact location and source point of the noise.
Yes, it seems like lifters but is it both banks? Is it lifters or bore scoring or just the exhaust expanding with heat or a loose spark plug ?
Whatever , the fix is time consuming and the parts expensive. So diagnosis is key to avoid wasting time & $.
When you get the cams off and extract the lifters, you need advice on what to look for to confirm you found the source of the noise problem. Can you imagine a re-do ?
The tappet inside the bucket may be jammed in the fully compressed position or it may be weak. In theory , prodding a weak lifter tappet with a wood dowel should give you a clue about which are weak/strong. Be sure to put each lifter in a designated storage box(egg carton?) so you replace them in the same position if they are still good.
If they are the original lifters and the engine is over 80K miles I would replace anyway - you've gone that far.
The lifters used to be very expensive but now the Interchange manuals have caught up with INA and you can find a BMW cross reference that allegedly is the same as the Porsche part. $21 each x 24 =!
But if you google the INA interchange part they are $12 each ! Heluva difference on 24 !But verify the number before you buy :
INA - 11321748884 or 4200049100
The Porsche price is around $70 each .
You should be able to get all 24 for less than $300 delivered with tax minus a discount.
Yes you can do this job with the engine in place but as an expert (Not me) said - "it's like building a ship in a bottle'.
The pioneer of this job was Doug Harn - google for his and subsequent posts on the subject "Dharn" is his Forum name.
In theory you can try some snake oil treatments Motor Medic, Rislone.... see Youtube.
Also on You tube ,there are plenty of sound clips for Boxster/996 lifter noise for you to compare with yours.
There is also an issue with wear in the lifter carrier. You'll know the carrier was worn because if you put new lifters in a worn carrier the noise will still be there/will return quickly ! In theory you can measure the bores in the lifter carrier for ovality/taper.... but there are no specs.
Replacing the lifter carrier gets expensive.
https://rennlist.com/forums/996-forum/623466-lifter-noise-2.html

I'll admit - I don't really hear anything that I can pick out as a knock in the video and I didn't hear anything that sounds like a stuck lifter.

Can you make a recording from under the car (or where ever the sound is clear) rather than in the drivers seat?

Maybe I attended too many rock concerts in my youth? :)

Maybe we went to the same concerts?
I have just been working on this issue using an Engine Ear, old style stethoscope and screwdriver. Even with the Engine Ear it requires lots of different positions, volumes,engine speeds to make an informed diagnosis. Even then, is it a lifter carrier issue or a lifter(s) ?
You need to discern the smallest changes in noise volume.pitch and frequency . You need to use both ear buds and really concentrate & repeat. Even using a smart phone microphone as close to the cam cover underneath the engine would be difficult in the early stages of lifter noise development.

IMO the knocks at 4 and 6 seconds into the video are not lifter noise.

doesn't sound tied to rpm? perhaps transmission related?

In which case an Engine Ear or even a screwdriver would quickly confirm the location of the noise

It's alright guys, found the issue. It's the water pump on its way out.

Some guys on the UK Boxa.net pointed me towards that issue, and after looking at several YouTube videos of other people with the same issue, it sounds exactly the same, and it's at 100,000 with the original pump.

New pump will be on its way soon. Thanks guys!

check idler pulley bearings & ancillaries also .