I installed a Gibson replacment muffler (#788200 2-1/2" inlet/outlet,19" body length) on my 1997 F-150. I kept the tailpipe diameter to 2-1/2" to keep from losing too much low end torque. I did notice a slight loss as it unlocks the converter on some hills it didn't do with the stock exhaust. The sound is very mellow even at full throttle. The truck pulls a lot stronger under full throttle up to 85 mph. I got it thru Summit racing for $73.21. My exhaust is run out the side behind the rear wheel.