Wrong ..I've had aftermarket exhausts on most of my previous cars.
This is the first I've chosen to just swap out exhaust tips because I could care less about making a 6cyl SUV any faster or louder.
Sounds like you had other variables that contributed to dropping .8 in the quarter mile. According to an online calc that means you picked up ~35hp by adding an exhaust that you cut and pasted from a Jeep with 6.4 liter engine.
Good luck in fantasy-land.