Alright all, bear with me, my mind is a complicated thing For the time being, I'm going to look into 2.5" High Flow Cats to go with the 2.5" factory tubing and maintain the deleted Resonator. In what is sure to be a long process in modifying my Viper, I got into thinking more about my exhaust system (Mopar Cat-Back is all), love the sound. I'd love to add headers in the future which I've come to find all have 3" collectors. To hopefully maintain at least the visual compliance with emissions, new headers would then lead to 3" High Flow Cats and associated piping. Where the "problem" lies is the 2.5" inlet of the Mopar Cat Back. I want to avoid swapping all the piping out. This got me into considering then how to integrate a 3" system to smoothly connect to a 2.5" system, which then got me thinking about Aerodynamics and Bernoulli"s Principle. My buddy's think that the constriction would cause the engine to work harder to force the same volume of air through a smaller pipe. But, air is a compressible fluid and as it draws into a constriction, Bernoulli tells us that the volume of air will accelerate as the air has to have the same volume on the other side of the constriction, hence the acceleration. So, my logic is that this setup will not cause much of an issue (maybe a small power loss is all, which I hope will be canceled out by the headers). If anyone has experience with anything like this, I'd love your input! Or if anyone has any observation I missed, let's hear it. Not sure how aerodynamic properties will apply to exhaust systems, haha. Until then, if this comes to fruition, I'll do what I can to get some dyno comparisons before/after as I'm very curious how this could pan out.