So, a friend of mine has a Z4 20i. It has the N20 engine. The car feels kind of slow and needs more boost. I checked and found that Kelleners retunes the it and bump the hp from 180 up to 220hp, but they also have a tune for 28i model which increases the hp to 294. Disappointing numbers, i know. But the goal of pointing this is since they are the same engines, why one is limited to 220 and the other is limited 294? I searched a bit more and found out the similar results from others tuners. The 28i makes way more power than the 20i.

Do the N20 in 20i and 28i actually differ from each other? First i thought the snails were different but they have the same part number listed on realoem.

Does anyone know anything about this?