According to that latest issue of Motor Trend, both (E90) 325i and 330i that are coming to the USA will use the new N52 valvetronic engine and both cars will have 3.0 liter engines.

The 325i will produce something like 215 hp and about 180 lb/ft torque and the 330i will have 255hp and 220 lb/ft of torque. The torque curve is very beefy and comes in earlier and sustained longer throughout the RPM band vs. the outgoing M54 engines.

The difference in HP/Torque is accounted for different intake system. The 330i will have a 3-stage intake induction system and the 325i will only have a 1-stage intake induction system. Of course, engine management software will be different for both engines.

The N62 produces about 13% more power and 12% better fuel economy because the various new technology including valvetronic. The magneisum valve cover also makes the engine weigh less.