I don't think cat location really matters - i think its more for "space management" reasons that these days car manufacturers are putting the cats right up close to the engine. Go back 10 years and lots of cars had the cat located under the cabin (Jap cars especially).
Moving the cat further away from the turbo will get that heat and restriction away from the turbo (and the rest of the engine).
On the Mk5 and Mk6 Golfs (im talking GTI and R's here) they have a cat right up where the turbo is (similar to your 118TSI but its not as big) and then another cat located under the cabin - so they use 2x smaller cats rather than 1x big cat. So for these cars, most of the aftermarket dump pipes just use 1x small hi flow cat thats located under the cabin.
Moving the cat further away from the turbo will get that heat and restriction away from the turbo (and the rest of the engine).
On the Mk5 and Mk6 Golfs (im talking GTI and R's here) they have a cat right up where the turbo is (similar to your 118TSI but its not as big) and then another cat located under the cabin - so they use 2x smaller cats rather than 1x big cat. So for these cars, most of the aftermarket dump pipes just use 1x small hi flow cat thats located under the cabin.
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