2006 chevrolet cobalt ss 2.4L non supercharged "muffler"?

[Matthew Tait]

i called napa and all i wanted was just the magnaflow muffler and they could only find it in a package as the whole pipin system right from the headers . but i found a magnaflow muffler at Canadian Tire for 130$ i was wondering if i bought that would i lose horsepower? changing it from stock muffler?