Thanks for all the reply's everyone. Let me explain why I believe I was losing torque. When I put them on my 2011 I could feel a lose in my get up and go the first time I took it out, I convinced myself that the added nose from the axle backs was just tricking me and I live with them for a year. In June of this year I took them back off and put the factory muffler back on the car before I sold it. As soon as I took it on the road I could feel how mush faster the car felt off the line. So I talked to my Brother a licensed mechanic and a friend and they both told me the same thing. They told me I was losing torque because the axle backs were putting out more air then the factory muffler but the factory air box wasn't taking any more in then it did before and I need a cold air intake to avoid losing any torque.