
If you don't mind me asking. What is the intended purpose of you modifying your vehicle. Race, Street, or Bragging rights?
My primary goal is to have a true 12 second car. I don't want to go faster than that. I drive me car on the highway and have to be realistic about it.
To keep a little low end torque you need a little back pressure to maintain drivability.
Talk to engine builders and pro racers to get a better insight on this whole exhaust thing. Let not get too crazy for the street.