I put a google.com head package on my car and dynoed it and it was adding 45 hp to the wheels. the car runs great and got better gas milage. It has tons of power from med to top end power. I last week put on a DC 4 to 2 to 1 header on my car and lost a couple of hp at the higher RPMs. I have now herd of this happening because of to much back preasure. Any thoughts.

*edit by e3NiNe ... non-vendor.