[JuliusB58]

I bought my car with an highflow downpipe in my M240i that has an opf filter. But I later read that you shouldn’t change downpipe on your car if it has an OPF filter on it. But my question is, is it possible that it has been hollowed out so that the filter is not there anymore? Does anyone have a opf car and can tap on it with something so I can hear how their filter sounds when it is still there? I used a hammer and gently tapped on mine but I think it sounds hollow but I need someone to help me decide!