HI all; One thing I have not seen mentioned in this discussion is balance. I refer to the intake side of the engine. The original air cleaner on my Imperial had one very small opening about the size of a quarter. It has a single 2 in. exhaust. It seams very restrictive to me. When changes are made to one part of a system, you should consider the effects on other areas. I use an open element air cleaner on my car and should have improved the exhaust system at the same time. Time, weather, and $ prevented doing everything at once, so I will be putting dual 2.25 pipes and the new 50 series flowmaster mufflers on when I can. I will use a crossover pipe (maybe an x system) if I can fit it in. Just my $.02 Larry 67Crown 4DRHT