I just removed my exhaust at my uncle's house, to gain access to the transmission, and I had to drive back home with no exhaust. Holy (place every swear word here) my car was loud! It gave me such a headache. It scared the crap out of me and I was out of it when I got in my house. My car sounded terrible as well, like a 90s honda with a ricer exhaust.
I was running an open header like ACSchnitzer was in his video, but my car has stock cams, and didn't sound like a harley (the idle was stable). Everything vibrated during the drive home. It felt like someone had installed a massager in my seat, dashboard, and chassis. Very scary. I couldn't tell you about the power, because adding one more bit of gas made it like 10 times louder, and I only revved it to like 3K. DO NOT RUN OPEN HEADERS! You will not be pleased.