Both my 330xi’s have folding seats and, while my ZHP definitely handles better, I can’t say it’s as noticeable as I’d have thought—given a 28% difference. Of course, I’m not pushing any of my cars to their handling limits. Tire pressure, on the other hand, I notice.
2004 BMW 330i ZHP (52k miles), Jet Black with black leather, MFactory LSD (3.38) with Z4 cover, 18"x8.5" ET38 APEX Arc-8's (Anthracite) with 245/40 Michelin PSS', Koni Sports with factory springs and front and rear reinforcement plates, Shark Injector, Corsa TSE3 cat-back exhaust, TMS under-driven pulleys (water & steering), CDV delete, TMS CF strut brace, K&N CAI, GAS DISA rebuild, TMS pedals, Wheelskins steering wheel cover, roller tray center console, black-out grilles, and WeatherTech mats