What would be the advantages/disadvantages of having stock exhaust manifold going to dual pipes and out high flow mufflers, as oppossed to stock exhaust manifolds to off road y-pipe to Corsa catback(though no cat) exhaust? As in, would the drop in back pressure be of any effect with the true dual exhaust? I plan on going to shorty headers soon, so either system would be easy to just bolt to the shorties.

 

Unless you need the clearance, I would go long tube headers with 3" off road y pipe into a 3" cat back exhaust. Better low end torque and I think easier to bolt up vs the shorties.