Most will install a fuel manager if they are having de-celleration popping in the exhaust pipes. They enrich the mix at lower speed to eliminate it. As far as performance gains, they are negligible. You can also eliminate most popping by changing the exhaust gaskets when you change or remove the pipes. They may look like they aren't there, but they crush so closely to the walls that it takes some work with a pick tool and lube to get them out. Also, aftermarket pipes have thinner exhaust flanges than stock, so when tightening them to get to 17 lbs/ ft, the acorn nuts bottom out before getting tight enough. This is solved 2 ways, either switch to a regular hex nut, or place a SS flat washer or 2 under the acorn when tightening. Then run a tank of fuel through her and re-torque. Those aftermarket flanges can also become bent or curved if not installed right, make sure they are perfectly perpendicular to the pipe. A friend to help support the end while you put the flange in a vise, and a big pair of channellocks or vise-grips will straighten it.