This has to do with a 2005 Impala 9C1(cop car package) with a series II NA 3.8 with the u-bend in a single outlet exhaust. This car is a friend of mine and seems convinced that he will gain power from putting on a cat back dual set up. My question is will he gain any power? Is his exhaust similar in that his will flow and lose no power up until 350whp mark just like on the grand prix's? He plans on the following mods: HV3 PCM Plog DP and KandN CAI. Will he lose anything on his current exhaust or is the cat back worth it for him with those mods installed?