Check out this thread for your answers.
Go here for Modding info.
zerothread/207927
NONE of these mods will void your warranty unless you damage something when installing.
There will also be a link there for exhaust soundclips. You can also check out the Members Rides thread and look at other Members signature's, people usually include their Mods. there.
I personally went with JWT Popcharger and Stillen Exhaust and have no regrets. Unless you submerge your car in a lake, you're not going to suck up water.
Let us know what you decide and if you have any questions after you have researched these and narrowed your choices down!
Good luck!