For the cupra (inlet and outlet on the same side) I always thought the vertical core sinlge pass (like the APR one, and I remember seeing another one with cast end tanks somewhere) was a nice solution.
APR seem to use the same/similar design on the A4 Stage 3+ kit.
I've no facts or direct experience though
APR seem to use the same/similar design on the A4 Stage 3+ kit.
I've no facts or direct experience though