[powers2]

I can answer the 1st question! Its 80mm ,as can be confirmed here
Novitec | Giulietta | Exhaust | Squadra Sportiva e.K. , Alfa Romeo , Abarth , Fiat , Ferrari und Maserati Tuning

 

[powers2]

Ovale is nearly right ,its oval.Hope someone will post a video on those exhaust systems ..