That makes sense. AFAIK the main difference between a stock and a "free flow" exhaust is the pipe diameter at the bends. I'm pretty sure my Borla is the same diameter as stock, but the diameter stays consistent throughout. I think this is called mandrel (sp) bending. This is what makes the extra power without losing your low end. No kinks where they bent the pipe.
I didn't worry about the pipe size. I just called Borla and told them what I was driving and they did the rest. I immediately noticed that the engine was breathing better after I installed it. Definitely a good mod, plus it should out last the truck.
Of course with the 2.7, I had nowhere to go but "up" with the power <img src="/forums/images/graemlins/smile.gif" alt="" />