In there own way , they all mess the Engines up , Engines when running need the Exhaust gases to leave the Motor easily , But the new Silencers have plates that slow or block the gases from leaving quickly hence the Silencers , Pipes get very Hot
The DEP shows a lower BHP output at hign revs , which if you are a Junior should not be too noticeable , if you can get one at the right Price , I`d get one , BUT the BSPA could well change things again next Year !!
Lucky