I cant see any real BMW drivers giving the advice that a remapped 320 is possibly in any way comparable to an M3!
Personally, after having a bit of unintentional rear end slipping action in my e46 M3 a month ago, has told me that to go alongside an engine producing a MASSIVE amount of power, you need equally competant brakes, suspension, tyres, differentials, stability and traction control (if your into that etc) to actually keep you on the road if your doing anything other than driving in a straight line down an empty motorway ..... Even if a 320 got a big boost in power from a remap, i'd be worried id put it in a ditch with vastly inferior '320 spec kit' that you still have in that car. Its hard not to get caught up in playing online numbers games where people look at BHP figures and remaps and exhausts trying to take a bog standard cheaper spec car and bolting on bits in some kind of effort to bring them up to spec with their pricier cousins. Granted theres a lot you can do with aftermarket kit but with this advice about remapping beemer 330's or doing screw modifications on old peugeots and wonder what the end product car actually is like to DRIVE? Can a 335i with the same kind of engine output as an M3 actually do the same thing on a track or a back road that the M3 can?
Im a huge alfa fan, having come from a GTV before my M3, but until they bring out a RWD car i can only ever think of them as very stylish everyday cars ... not 'weekend motors' i dont think.