GSXR1000

just bought a 2001 GSXR1000, 4500 miles, origanal owner, older guy, bike is pristine looking with an extended warranty. It runs fantastick, much power, way fast, I have been riding a hundred HP Harley for the past 5 years, what a difference. I have a few questions/concerns about the GSXR1000 that I hope somone will be able to help me with. 1) Sometimes when I take of it feels like the clutch is chattering. 2) The transmission whines in lower gears and makes some pretty loud bangs when shifting. 3) I would like to lower it a little, any reason I should not? 4) What is the best sounding/ performing aftermarket muffler for it? 5) What is the best motor oil to run in it? Thanks in advance for everyones help. I live in South Fkorida and would like to meet people to ride with, all my friends have Harley's, too slow!