Let's use the inlet on the right. If a hole or slot is cut in that pipe just inside the muffler where the arrow head is, the exhaust gases will flow through the hole then follows the path (4) out the rear. You can't see pipe (4) because it's under the others. That bypasses the entire muffler.
RichS

Ok, I think my "drill a hole inside the muffler" project was a waste of my time and a little cash. I think it sounds a bit louder, but now I'm thinking it's wishful thinking.

The reason I say this is my friend borrowed my long nose grinder and put FIVE holes in each side and it sounded no different than stock.

Sooooo, we're both gonna get a welder to put on the 1 inch bypass pipes and see if that makes for a nice loud exhaust note.

Oddly enough, I'm starting to feel a little like a ricer.