Guys, you can not believe. But facts are facts. This weekend will be reflashed int0 328 for about 10 cars. Reflashed 320xi goes on Dyno on Wednesday to see the real result. But the drags with 328 shows that speep of reflased 320xi is the same.
The White one is reflashed 320xi. The Red one is 320i stock.
Reflashed 320xi vs. 328xi stock with downpipe.
Surely your tuner can also make this procedure, but apparently there are questions the legality of the use of original firmware BMW.