When I use to inspect vehicles back in the 90s all you had to have was the pipe a little futher back than the cab of the truck. You didnt want to see if it improved performance and or fuel economy?
Before I got a friend to weld me up a straight pipe exhaust in place of my muffler on my insight I unbolted the muffler and drove it around a bit. It wasnt that much louder and gave more low end torque, plus a nice deep throaty sound.
