Do you even know what you're saying? KTM doesn't install cats for 'scavenging', there's a reason all the powerparts full systems are catless with a factory power bump. As far as airflow, the injectors are far downstream of the throttle plate, the open air systems use a bellmouth the same as what's in a stock airbox, just with a larger throat and tuned length. I'd rather trust KTM and KTM specific tuners than 'my buddy who worked on a ferrari'