After 700 miles with air intake and flowmaster delta 50. Power up, most noticed at mid to hi rpm. MPG came up from 23.7 to 24.3. The sound of the flowmaster delta 50 is quite nice. Not to loud inside, yet a nice mellow bark outside. The above mpg is normal drive to work speeds. Interstate 70-75 mph, some side roads 55-60 mph. Hot temps 105 to 110 with ac on. In Phoenix, Az. area. This is leaving the stock pipes and just adapting the 2 1/2 fowmaster up and down to the exaust system. I really hated to trash the new exaust altogether!! So just the muffler went.... I would reccomend this combo not very expensive, with very satisfactory results. Would guess 5-8 horse power gain and a little better fuel economy.