After doing so many custom exhaust cars so many years you kind of live and learn,many might disagree with me but many of these muffler shops charge as much as the dealer in labor for a cutom exhaust,then its time consuming to bend those pipes to stock specs and lots of welding involved,compared to a direct fit exhaust thats precisely made for your vehicle,example the Corsa made of stainless military steel direct bolt on took less than an hour to install with no drone and any kind if vibrations or rattling you might get in a custom exhaust setup,just my 2 cent.