After doing the O ring mod last year I'd noticed it was still leaking so after taking it apart and measuring everything I'm not convinced the O ring mod is a fix. The 'nose' of the TB housing is 81mm dia and the inner dia of the elbow is 90mm so it idealy needs O rings 80mm inside dia and 5mm thick to seal between the TB nose and plastic elbow. Something like this may work
https://simplybearings.co.uk/shop/product_..._id=515248
or these
https://simplybearings.co.uk/shop/Seals-O-...er+O-Rings
Also the slots for the OE seal retaining ring are likley a source of leaks so as I'd removed this I wrapped some PTFE tape around the groove and then put 4 of the O rings in there to seal it but it could be done also with a zip tie. 2012 TDV8 Vogue (L322)

The metal retainer - at least mine - doesn't look like to be made of strong spring metal.
IOW it bends out of shape easily.
When you fit the metal retainer without elbow, do all the tabs sit snug in the groove 360 degrees?
No wiggle?
If not, bend it back in shape (smaller diameter) to make sure all the tabs click in.
Thing is, in my opinion, bending it in shape and testing it and then removing it bends it out of shape again.

I've tried fitting the metal retainer in the elbow before mounting the elbow but that didn't work for me.
The workshop manual shows to remove the retainer as step 1 and doesn't show to fit it before mounting the elbow, they say 'assembly is in reverse order' iow push the retainer in last. 2012 4.4TDV8
2000 Honda S2000

I adjusted the retainer and it fits fine - a bit fiddly but if you do itwith the elbow off the car you can see when it's right as all the ends stick through the slots evenly. If you are worrid about this comming off it would be easy to put a large zip tie or compression clamp around it. 2012 TDV8 Vogue (L322)

This should fix it.....

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Click image to enlarge

Blimey, I know the hose is expensive at £217, but don't you think it's time to admit defeat and just buy the proper part? Considering the price of other parts for our cars it's not the most expensive of items.

As I said the bigger O rings at <£7 would probably do the job just as well as long as you can seal the sealing ring retaining holes but as I'd bought the coupler I thought I'd fit it anyway. Also the standard seal is not very effective and as mine has a damaged TB 'nose' it would not seal properly anyway. 2012 TDV8 Vogue (L322)

Should have waited until the T bolt hose clip arrived.........

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I replaced mine with a new genuine hose back in February, was £207 but if it lasts as long as the original did then it’s worth doing it properly. Also I’m not worrying about it leaking with a diy fix.