I’m posting this here hoping to save someone else some time. I found most of this from the link below, by a strike of luck – the article is in German and does not show up in google search results.
The 944 throttle body tends to develop a vacuum leak at the butterfly valve axis seals. Replacing the old seals with o-rings is possible, but not the right solution. The original seals are radial lip seals and replacing such seal with an o-ring may work for a while, but this is not the correct solution.
The correct way is to replace the entire bearings, which include the seals.
The original bearing (INA F-95775) is no longer available – or perhaps it was never sold commercially. The current equivalent is the HK 0810 RS. The HK 0810 RS has a single side seal, like the original part. The HK 0810 2RS has dual seals and can be seen as an upgrade over the original parts.
These bearings are readily available from a number of different manufacturers.
The large o-rings should be replaced while the throttle body is off the car. I tried looking up cheaper replacements, however the original Porsche parts are actually reasonably priced – no reason to go aftermarket for these.
Part numbers:
Round seal 82 X 2,5 – 999 707 036 40
Round seal 65 X 3 – 999 701 331 40
There is also an o-ring at the TPS, that you may want to replace while you’re in there. I will update this post when I have found the correct replacement.
Disassembly is mostly straight-forward. The hard part is removing the bearings. An M6 expanding brass anchor can be used to remove the old bearings (see link below).
These look suitable (M6 version): https://www.aliexpress.com/item/1005003512118808.html?spm=a2g0o.cart.0.0.35ff38datIqRmb&mp=1
When reassembling, the throttle plate screws must be secured. This can be done either by using split end screws or by using a high temperature thread locker.
The 944 NA and Turbo throttle bodies differ slightly (I believe one of the bearings is already a dual seal one) but as far as I know, they use the same bearings.
Removing the throttle body will let air into the coolant system, so the coolant system should be bled after the first test run, in case air bubbles have collected in the cylinder head. I also recommend a pressure test, to verify that there is no external or internal coolant leaks after mounting the rebuilt throttle body.
Source: https://www.stinni.de/index.php/porsche/drosselklappe
