Euro M3s received the high-output S50B30 (286hp, ITBs, single-VANOS) and S50B32 Evo (321hp, ITBs, double-VANOS, 6-speed) engines, while US cars received de-tuned S50B30US (240hp) and S52B32 (240hp) variants with M50-derived hydraulic-lifter heads; the difference is widely characterized as the gap between a 'real M engine' and a market-driven compromise.
Euro-spec S50B30/B32 versus US-spec S50B30US/S52B32 engine differences
BMW E36 M3 (US-market, 1995-1999) · factory-spec