MadRussian's post may have been written in 2004, but what he says remains essentially correct. There is still no cheap or easy way to get more power out of our M3's, and software upgrades, intake manifolds, and exhaust mods won't get you much, if any, additional grunt. At its essence, an engine is simply an air pump. It produces power by bringing in a 17.1 to 1 mixture of air and petrol and combusting it. Power is limited by 3 things. First, how much mixture you can get into the combustion chamber and combust in the shortest period of time, second, how quickly you can evacuate spent gasses from the system so that you can start the process all over again, and third, how efficiently you can turn the petrol and gas mixture into usable power. The M3 engine is ultimately limited by its overall capacity of 3.2 litres. Absent forced induction there is a limit to how much fuel and air mixture can be taken into each combustion chamber (which is why the old racer's adage has always been, "there is no replacement for displacement."). While the current redline might conceivable be raised, it would be quite costly to make certain that the engine wouldn't self-destruct, and maximum power comes at 7,900 rpm anyway. There are no major restrictions in either intake or exhaust that impact power production. What does this leave you? Either forced induction (which WILL give you a substantial boost, albeit at a substantial price) or finding some other way to increase circulation. This would mean a completely new fuel injection system (it would need to be direct injection), different intake, and completely different computer programming. By the time all of this is done, you will have spent at least as much as a good forced induction system would cost, but without as much gain. While technologies change, the laws of physics don't.