One more thing also, why does BMW, and generally car companies, make a engine, which restricts air flow and power? Obviously cats in place are for emissions, smell etc, but things like the headers, yes they can be catted and still deliver better flow?
FMIC for instance, why is the stock one so small? Surely a turbo motor would run more hot, and cooling would be preferable to a higher level?
The only real reason i think its that technically OEM parts make the engine run at the factory level it should be, for safety, safety of the tranny i guess also.
Sort of answered my question but just wanted your thoughts?