I did a completely open 3" system at one point two years ago and it was awful.... I have the 42DD Catless RACE TBE, so basically its 3" all the way back with a single Magnaflow 40 series muffler, and thats it. Its loud as hell when you're on it, but still nice to putt around in, and no drone at highway speed.
I called 42DD up and asked them to make me a section for the rear of the car to replace the muffler section that was just straight pipe. So now the exhaust would be straight through , no res, no muffler, no cat, no anything... Installed it, drove 500km on it, and immediately hated it.... It sounded great down low, and was super aggressive, but it droned like NO OTHER at highway speed, so bad that I would get headaches.... SO, I would advise against going straight pipe.... Not to mention theres no tone that you would get from a muffler, and honestly these cars sound ricey af without a muffler, or a resonator....
