Can't help with the pipe question. Mine has a Yosh slip on and I think it sounds great. Not really sure why so many riders take pot shots at the Katana. My 01 750 is my first bike and I've been very pleased with it. I know it will not be my last bike but it has been great to learn on. 6 months and 3500 miles have put plenty of smiles on my face. I guess the riders that take shots at our Katanas actually think that we really care about their opinion. I for one don't, I'm in this sport/hobby for me not them. I'll step up to a more powerful bike when I'm ready and this will be determined by me not by anyone else.
Enjoy your bike and ride safe.