Group n systems are rally exhausts. I have never seen the hype about them because all they are is a straight through exhaust. No centre silencer.
I have had 3 cars without centre silencers and de catted and tbh they sound mint, all that popping and gargling.
However on a motorway I could not stand the drone!!!
Absolutely horrible, I really would not recommend an exhaust with out the centre resonator on a daily. It is soul destroying and will deafen you.
I hope this helps.