Adam speaks the truth on the sonic output of a UFO product, they are loud! I have the UFO 4/1 Dragstar, and had to do something to quiet it. Read the posts:
http://www.vmaxforum.net/showthread.php?t=31804&highlight=frankencanister
The advantage to this mod is, not much $, much quieter, allowing you to use your performance without alerting every LEO (law enforcement officer) within earshot that you're winding it out, and you retain your hearing, since you can do permanent damage after one exposure if it's severe enough. You will need earplugs if you buy this, the stock 4/1 or risk damage to your hearing. That, or modify your system along the lines of what I did.
If you read the thread, you will see that I tried the UFO megaphone in place of the shorty 'balogna-cut' angled end tip they sell the Dragstar 4/1 with. Still mighty loud, still need earplugs. But quieter than the angled end tip.
I like the performance of the 4/1, and w/an appropriate canister, you can ride without earplugs. I didn't have to change the jetting with the system I made, after I installed a Dynojet Stage 7 kit, and then came up w/two different canisters to add to the UFO 4/1 to keep my hearing. I can swap one for the other in about 20 minutes, or go back to the balogna-cut UFO, or the UFO megaphone.