Note:  This worked on my son's 1997 Sportster and should work on any HD mufflers.  You'll need to examine your pipes to be sure.  Just opening up the baffles should not require and re-jetting or carb adjustment other than maybe adjusting the idle speed if it speeds up a bit as the engine breathes better.  Fuel injected models should automatically adjust to the open mufflers just fine.

Your stock HD baffles are welded in and not the same as the baffles in the guide about aftermarket baffles titled Baffle Mod Instructions.

Here's how we opened up my son's stock pipes on his 97 Sportster.

1st we looked up his mufflers with a strong light. It looked like he had a central perforated tube with a plug at the end.

2nd we removed his mufflers.

3rd we stuck a dowel up the muffler to see how far the plug was from each end, inlet and outlet. It turned out that the center tube ran completely thru the muffler with a welded plug like a nickel right in the middle. The plug forced the exhaust thru the central tube holes out and around the plug then back into the central tube on the outlet side of the plug.

4th we used a piece of 3/4 inch pipe about 3 feet long with a big hammer to knock the plug out of the pipe. It looked like what we used to call a slug, a piece of metal about the size of a nickel or quarter. This opened up his pipes so you could see thru from end to end. The baffle was still in place so it wasn't extremely loud but had a nice deep rumble.

Last we put the mufflers back on the bike.