I noticed some exhausts... TME, JETEX,etc...have dual pipes coming back from the muffler. Is there any benefit or negatives to doing that over the single pipe with single tip? Different air flow or sound?<p>Also, I love the 3" EVolve exhaust but am concerned with the ECU upgrade. Do I have to match the ECU upgrade with the exhaust? For example Rica uses 2.5" Ferrita, but could I also use Jetex for example?<p>Also, IF I were to go with a 3" Evolve exhaust and use the BSR PPC ECU upgrade...BSR specs it for a 2.5" exhaust. So this would not be a good thing for me to do?