Ok I just had my new cat back exhaust system put on my SL in place of stock back in february. My problem is after i put the exhaust on i noticed a horrible low end loss of torque. The loss is very evident on the car. It takes off horribly slow. Now I am trying to find out the problem of the system. The system includes 2.5 inch piping from the pre cat all the way back with a resonator in place of the cat to quiet things down. After the resonator it runs into a 2.5 single in dual out FLOWMASTER 50 series muffler. Out the outlets it runs into a dual setup. Now is my back pressure problem probably:
1. 2.5 is too big, should get new piping (2 1/4)
2. the new resonator i had put on to quiet it down, very baffled.
3.the FLOWMASTER 50 series muffler itself.
4.runnign dual exhaust