should I install aftermarket muffler?
How loud did you expect it to be? The Magnaflow is one of the best cat back systems you can get for the Mazda 6. It is one of the best sounding and best tuned systems aside from Injen and a handful of other select companies. Since you already have an entirely aftermarket system from Magnaflow, the mufflers are already aftermarket. In my opinion the last thing I would do is replace those units with something else on a full cat back exhaust. If you want your car to sound loud and drive you insane, take your mufflers off the 6 and see what happens. From experience with my Mazda 6, it should drive you mad. Of course, engine sound also depends greatly on which engine you have. The 2.3 I4 or the 3.0 V6. If you really wanted loud, you should have gone with Tanabe USA's system for the 6, which is basically one series of their mufflers modified to fit from the axle back. It would have saved you a lot of money too.
The reason is you only went slightly bigger then stock. The stock exhaust was likely 2.25 inch and most of the Magnaflow systems are 2.5 inch. A 3 inch exhaust would be louder and cost more to purchase. You should now have a cold-air intake installed to take advantage of the airflow in and out.
Why would u want a loud car? To be an annoying ********?
