From what I have read it shouldnt really change anything but the sound, kinda like just running a straight pipe. Now if you take off the cat then you need a PC.
Ok, I just ordered a Competion Werks Ti slip on and thats going to be the extent of my engine mods for awhile and I dont really want to buy a PC at this time for just a slip on.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.