E30 Zone

hi i have 325i engine and someone before me put a 320 manifold.. not sure why.. but is it worth me putting 325 manifold back on on a perormance stand point? also if i do will there be any other parts i need to change?
thanks

A 2.0 manifold on a 2.5 head will strangle the engine as the ports are much smaller on the 2.0 item. Which throttle body is attached?