Below is what A.W.E ppl told me why they're better than GMG.
" We chose to use just one muffler to save weight, keep costs acceptable and get a better sound from the car. There is no real need for two mufflers. I have not heard the car with two mufflers, other than stock, but I can only imagine it greatly cuts the sound down and restricts flow. Adding another muffler seemed like it would be over kill for what we were looking to accomplish. That was more power, less weight and a great muscular V8 sound. Have you seen the performance gains and heard the sound clips on our web site? Mission accomplished!
You will see other systems talking about crossover tubes. We use the forward positioned muffler to achieve the same effect as a crossover would. By having both pipes come into one chamber, the pulse pressure is equalized thus reducing the harsh sound like a straight dual system would have. This also lends itself nicely to the perfect sound coming out the tailpipes. That equalization also improves overall flow and performance.
We have engineered out exhaust to be a perfect direct bolt on upgrade. All factory hangers are used and no permanent modifications are made to the car. You can go back to stock at any time.
If you have any questions, please do not hesitate to contact me.