So as some guys read I got new Catco cats put on this week. Installed at an exhaust shop with experience and my brother who took it for me said they told him it is misfiring(car) after they installed them. Before the old ones never made noise as loud as these but they were also clogged. So my new ones make a rattling noise that isn't too loud but can hear it from inside with windows down. Plus the check engine light was one till I revved it a couple times. So is there really misfiring and maybe causing the noise? SN: when I go fast on highway it feels like it lags to go into different gears when flooring it.