I have instaled an after maket header and a high flow muffler in the anticipation that it would also help fuel economy. My engineer family and friends pointed out that the throatle plate is the biggest restiction in the system and therefore even if the system has lower restiction then the stock setup, it only matters at wot, when using the maximum fuel! I use the exta power about once every month or two for seconds at a time. Not the smartest thing I've ever done.
