Which of the Gibson catback systems would be the best for the 4.2L in regards to performance? In other words, which one am I least likely to lose low-end torque with, while possibly improving power at the same time? I've pretty much decided on a Gibson system, but don't know which way to go. Single 3" side exit, super truck, or sport truck? Any experience with any of these on a 4.2L would be helpful.