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
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.