Tke it from me who just did a plethora of exhaust mods.
There is an important reason Ford chose to include two mufflers in the design of the Mondeo exhaust system. Ehaust noise is generated by the air leaving the exhaust valves in an internal combustion engine. The 16valve 4 cylinder and the 24 valve V6's have two extra valves per cylinder over their normally aspirated counterparts. The middle muffler is nescessary to remove the rasp and to help quiet down the system. I'vbe tries the single muffler setup and it sounds like crap. I replaced my resonator with a straight through tubular muffler not a glasspack. The reason is simple glasspacks never last. Car sounded a bit deeper on acceleration and was a little quicker. Then I got "hack happy" and cut off rear muffler. That was a bad move. The drone on acceleration was driving me mad. I couldn't take it..so I went to a custom exhaust shop and had a short, 12" high-flow turbo muffler put on rear with a dual chrome tips peeking out from under the bumper. Looks cool, sounds great and has much better flow.
