The OP is a little hard to read, but it sounds like your dumping your exhaust at the Y pipe? I have had to sawzall my exhaust off at that point once, because a wreck bent my muffler up into my bumper. Not only is it MUCH louder, but like these fellows said, you will lose a considerable amount of torque. To the point where it is noticeable.
If you are going for sound, and trying to maintain performance I recommend retaining your stock catalytic converter, purchasing a high flow resonator, and running 2.25 piping to a single muffler. That is what I am currently running and it is not loud (pending muffler, I am running a Apexi WS2), but it certainly has a growl, and you do not sacrifice power.