D.I.Y Exhaust mods???

hey guys...
few questions to ask in regards to exhausts. firstly, is it legal in nsw to cut off ur exhaust completely??? i noticed alot of racebikes with them completely chopped off? makes the bike very loud... loud is good! will it effect performance/engine in anyway? secondly, how can you shorten a pipe at home? is it a matter of chopping part of the pipe out? and again, will this effect performance/engine in anyway??
cheers
few questions to ask in regards to exhausts. firstly, is it legal in nsw to cut off ur exhaust completely??? i noticed alot of racebikes with them completely chopped off? makes the bike very loud... loud is good! will it effect performance/engine in anyway? secondly, how can you shorten a pipe at home? is it a matter of chopping part of the pipe out? and again, will this effect performance/engine in anyway??
cheers