Update... UFO Street Pro sounds AMAZING!!! Little bit of a pain to install but well worth it! Best money I've spent since buying my Max.
If that's your belief, try to find someone near you who has done a radial tire switch. You won't believe how it changes the bike's dynamics. When you hit triple-digits, the radials eliminate most of that trepidation from the stock bias-ply tires as the bike would start to bob and weave on the bias-ply tires. You would have to install a pair of clip-ons to get out of the wind blast to really feel more-comfortable at those kinds of speeds. But, most of us aren't holding it at 8000 rpm in 5th for any sustained length of time, usually it's accelerate to a max speed and then back-out of the throttle to legal speeds. Still, radials will make those types of runs much more enjoyable, and safer.
unk:
I have a UFO Dragstar 4/1, and I like my exhaust quite a bit, especially since I made a canister for it so I don't need to use earplugs to ride it. If I had to prioritize between the exhaust and radials as the cost is roughly the same for either, I would choose the radial swap.
I included a set of pics of the Dragstar 4/1 going thru some changes, all-done this year, from initial installation before 2013 Daytona Bike Week, to a UFO megaphone (probably one of Jon Cornell's last fabrications before he died), to a literbike canister adaptation, which allows me to enjoy the UFO 4/1 scavenging, but w/o the excessive noise.