I could be out in left field, but I'm pretty sure a good set of slip on's are going to out perform a set of gutted stockers with lollipops bolted in any day of the year.
I won't disagree with that. Just throwing an option out there based on the title.
I drlled a 3/4 inch hole throughout the center of my stock pipes on my 48 and they sounded alot better. I was told from someone who had done this before me that he started at 1 inch and stopped at 2 inch. He lost bottom and according to him and wasn't pleased with the sound once he went larger than 1 inch. But if you gut a pipe you can get the back pressure by installing torque masters. I have 158w torque masters to try in my short shots without baffles when I get the time. D&K Customs told me I would get the best round and performance with those.
All i did was grind the weld out of mine and removed the baffles. They are loud as heck ! And they dont sound that bad either. Now its just a big hollow tube. And no the bike picked up power and im useing a VH fuel pack 3 .