I have a 1997 Chevy S-10 Blazer 4WD, 4.3L Vortec engine, auto trans., about 85,000 miles. In attempt to improve my gas milege and performance, I had a Flowmaster muffler installed. However, my gas milege has gotten much worse. With the stock muffler I was getting about 16 MPG and now with the Flowmaster I am getting about 12 MPG. I have a series 50 DeltaFlow Flowmaster with a single 2.5 inlet and a single 2.5 outlet. I just had a new catalytic converter put on and still suffer from loss of gas milege. I recently installed a K&N Air Filter to help with the airflow. It seems I have lost some performance at the lower end torque level but not at the higher.
Any help or comments would be appreciated. Thanks.