Artz, How much research have you done? What internal engine parts are different? It appears you have an awful lot of knowledge for someone who has so many problems with your other BMW's and Mini's. BTW your profile shows you are all of 21 years old. If that is true, coupled with your extensive mechanical experience you get by taking your vehicles to the dealer, I question the level of expertise you have to make these assumptions.
Here is what I know for a FACT related to the 325 3.0 vs. 330 3.0:
*The ECM part number is the same, software flash is different.
*Fuel injectors are the same
*Intake manifold is different- electronically optimized for various loads and RPM
*engine wiring harness is the same (that means if I has a 3 stage manifold I could plug it right in)
*engine short block is the same (this means all parts in the lower end are the same)
*Cylinder head assembly is the same (this means that the valve timing gear, cams, valves, etc are all the same)
*Valvetronic solenoid valve is the same
*The exhaust is different.
*Throttle housing is the same
I could take my 325XI, reflash the software, add exhaust for the 330xi, and add the 3 stage intake and you think I don't have 255hp by then? What makes you think the reflash wouldn't make a difference by itself?
Do you really believe that BMW would build an engine with different internal parts for the US only in the 325 only? The 2.5 is not available as yet in the current E90, but will be next year. Then the 325 will be a true 325, not a 330 in disguise. BMW had a marketing problem since they couldn't get a 2.5 into the US for the introduction. 325 is less expensive. How do they maintain the product? Stuff an existing engine in it, deduct 40 hp and sell it for less money.
It is very common for manufacturers to tune their engines differently for different applications.