i almost bought a high flow cat from random tech, and the guy who was the tech guy told me, the cat is only as good as the install. where did u install the high flow cat, and what brand is it btw? sorry if u stated it already, im too lazy to scroll down and check. cuz maybe it was installed poorly? many times when its not a direct fitted one, cuz many are universals, such as carsound. and u need to weld and cut, thus, sometimes they go bad easier if installed incorrectly or poorly.