Originally Posted by mojo_78613
I wonder why BMW did not consider using the N55 midpipe when this car was being tested and produced.....
The N55 was designed as a less expensive replacement for the N54. The mission was to duplicate the performance while reducing costs. Cats are expensive, so the N55 was engineered to allow the use of a single cat while still making emissions. Twin turbos and forged internals were also dropped for the N55, further reducing cost but reducing the strength and performance potential, which is why the factory chose the N54 as a base for tuning with the 1M.