mindmap, mikertroid. I’ve got the N53 detuned 3.0l in my 325i. In order to get to N53 330i levels of power (220>272bhp IIRC) you need the 3 stage intake manifold (325i is only single) which provides a slight forced induction effect by opening and closing valves in the manifold and changing the intake “length” through the rev range – this is the main piece of hardware that provides the extra 50bhp. I spoke to a couple of local tuning shops and they said a remap, exhaust and air filter etc. would get nowhere near 272bhp but would give better sound, responsiveness etc.
I really fancy getting the mod below:
http://mosselmanturbo.co.uk/remapping-carstyling-chiptuning/bmw/car-tuning/performance-packages/x/bmw-325i-e90-218hp/
£1500 sounds pricey but it gets you a 330i.. 325i’s are ten a penny in the facelift E90 but a manual box’d 330i with good spec is rarer that rocking horse droppings. I would get the mod tomorrow but for some reason the OH thinks it’s not a good way to spend 1500 quid!