[Bob Putnam]

The standard steel sidepipes have a fiberglass-packed muffler inside with 2.25" entrance/exit - no tapered transition. I'm sure there's some power loss there but I'm afraid the pipes would get LOUD if it was more efficient.

The stainless pipes are internally baffled and I haven't seen the details of the baffles.

I don't know anything about the HRE pipes. I'll ask Peter whether he's seen them.