I'm going to be doing cat back on my car. What do you think will give all round better performance dual or single exhaust, turbo or flow through mufflers, open up the diameter of the pipe. I don't want to lose the torque but if the horse power increase is that great that the torque loss doesnt matter i can deal. But I'd like some advise/suggestions and I know the 1999 duratecs exhaust is more restrictive. Sound isn't key here. Just want the car to be quickest it can be.