08-01-2015, 01:21 PM
I've had a Fiat Coupe run 250bhp on a 2" system with a standard cat and have seen a V6 Astra run 200bhp at the flywheel with a 2" system. It doesn't seem too critical. A civic type r (ep3) runs almost 200bhp standard and only has a 1 3.4" system from the factory.