Joined: Feb 2006
From: Round the Bend UK
I Ride: GPZ1100S, GPZ500S
I'm not a pro so will answer the best I can
1. it will hurt you eardrums - also see 3
2. race gas is usually necessary for highly tuned race engines, street motors don't usually need it unless you start changing things like compression ratios, valve timing.
3. if you start messing about with engines you need to be aware of the implications, as leaning out the mixture through improved gas flow will lead to meltdown inside the engine i.e. holed pistons, burnt valves etc., so be cautious before you start modifying anything. Go with the exhaust makers recommendations, though usually with replacement street systems no jetting alterations are necessary.