I'm going to also agree with the others. A loud exhaust won't make you seen. Even if it was loud enough to distract drivers from what they're doing, it can often just confuse them (they might hear you, but can't see you, and then it's a guessing game).
I had a Harley blow past me years ago on the highway. It was extreme. Loudest bike I've ever heard since. I still didn't "see" him coming because he approached me doing about 2x or 3x the speed limit wearing all black. I still couldn't hear him until he was RIGHT on top of me. Effectively, it went from completely silent, to mind numbingly loud as he passed by my car which completely shocked and disoriented me, and by the time I knew what was happening and recognized that a bike had passed me he was 100 yards ahead of me and I could barely hear him again. I don't know about you, but the last thing I want is for all of the cagers around me to be disoriented and confused.
Ride like you're invisible, wear all of the gear all of the time, and prefer bright colors for your bike and gear. It really goes a long way. I recently saw a video on YouTube where a guy was testing the theory of hi-viz. He set his camera up on the side of the street at night and rode by in several configurations. The bike was basically black. His preferred gear was black as well, including the helmet. When he rode by like this he was literally invisible. You could barely even notice him, despite knowing he was there because that was the point of the video. Scary. He tried with a hi-viz vest and black helmet. You could faintly notice the hi-viz, but it confused your brain because whatever "it" was it had no visible head. It sort of made your brain doubt that a person was there. Scary! He tried with a white helmet, and black gear. You could immediately spot the helmet. This was a big improvement over the previous configurations, but the bike and body were still invisible (but the helmet stood out enough that you could recognize that somebody was coming). Finally he rode by with the white helmet and a hi-viz vest and he was clearly visible. I already believed in bright colors, but that video did a great job of illustrating it for all of the non-believers. He said after watching it back himself he was no longer going to ride around with the black gear.
I just purchased a new jacket that will fit my beer belly, and since I couldn't find a white jacket that I liked (most of them were 70% black with white trim) I decided on a hi-viz jacket instead, which I am so far loving. My wife saw it for the first time when I was trying it on, and she said it was hideous and she hated it and didn't want me to keep it. And I said it's about being seen, not being fashionable. The size was wrong so I had to play a few games to try out various sizes, but once the correct size arrived I went for a ride. My wife was out getting her nails done so I decided to ride over to the shop to show her the jacket. She was on the second floor of a large building, and she said they all saw me coming down the road without knowing I was going to be coming. She figured it probably wasn't even me, but realized it was when I pulled into the parking lot. Pretty good result if a bunch of gabbing hens gossiping in a nail salon on the second floor of a building notice me coming (on a quiet bike) when they're trying to make each other pretty, not even looking for me and don't even care about bikes.