It will definately mess the tune of your bike up. And it will be very loud.
It can. But most slip-on's are designed for your bike and won't require tuning if you don't want. But it's always a good idea to get her tuned again if you do change slip-on's.So if you just change the slip on to a striaght throw pipe it will throw the tune off a lot? All I plan of changing is the slip on and dont really want to get a PCIII unless I ever do a header or more.