Let me know if 8 and 8A are the right size. I have ordered 8 (3C0145117H) a few times from the dealer, using my VIN number, and on each occasion the O ring has been too small.
That and the fact the engine movement wears the O rings out in no time (and also the internal bore of the metal pipe), I gave up and went with a 6R intercooler and the bayonet fitting cut off the metal pipe, and replaced with a regular 2.25" rolled edge pipe. I've not seen any oil sweats since
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Remember, if you see oil on those pipe joins, it means boost is leaking. The air pressure is forcing oil past the seal. It always was a sh*t design, purely for speed of assembly on the production line, but terrible sealing integrity. The problem is compounded by remaps.