Yes it did that, and if you tested the exhaust at idle it would have less emissions than without one, but the pump and all the other smog junk they put on robbed power thus more fuel was burned to get from point a to b and the cycle started again. Go from point a to point b and burn one gallon of gas at one pound of emissions per gallon or go from point a to point b and burn two gallons of gas at 3/4 pound of emissions per gallon. Less emissions per gallon but more gallons burned. But I don't think were speaking about the original question posted and I apologize.