I'm trying to design a straight back exhaust for my car. I noticed my diesel has two cats, a small one leading from the engine and another were the tailpipe juts out (just like in any other E46). I know I can replace the last cat with a exhaust sytem (such as an Eisenmann or a Remus) but does anyone know if I can remove the first cat? Will it adversely affect the car? I don't know the sulfur content of diesel in my country so is that second cat there to prevent any harmful gasses? Will an exhaust (catback) for a gas E46 work on my car? Is the clearance the same?