2004 FLSTCI, 1993 FXDL
By "nicer ride" I can only assume you mean quieter. On that Fuel Injected bike going back to stock pipes and not seeing or feeling a difference in power means to me it's never been tuned properly. Stock they all run really lean so your plugs probably look light in color giving you the impression they're okay. Do you have a Stage One and/or a tuner on it? I like your idea the back pressure is different but with that being said if they're the same P/N something is wrong. I have the same year/color paint scheme btw. Wish I'd saved mine so I could look at them now.