Suggestions on Changing Exhaust

[Sinker]

I have a 2000 Road King Classic with with the following setup:
-95 CI Kit
-S&S Gear Drive Cams
-Headpipes with cats
-Vance & Hines slipons
-Factory MM fuel injection
-Dyno tuned to pull it all together and eliminate the obnoxious popping and backfiring due to the MM FI.
When I did these updates I wanted fishtail exhaust but were unable to find any. Recently, I bought a set of used stock HD piples that have the fishtail ends on them.  I would like to replace the Vance & Hines mufflers with the stock pipes with fishtails.
-If I do this what can I do to make the factory pipes perform better?
-Would I need to have the bike re-dynoed?  I don't care about milking the last few HO and TQ but don't want to go back to the backfiring and popping the bike had before. Any words of advice are appreciated.
Thanks/Sinker

[kd]

If you have the parts, try them.  If there is no significant change that'll be a good sign.  An AFR test after on the drum won't be as expensive as a full tune.

[smoserx1]

I would swap them out and see how it runs.  Are you sure the headpipes have cats?  I didn't think anything had those back in 2000 except mufflers for California models.

[kd]

Unless they are 2010 and up OEM with the under the frame cross pipe to the left side.  Those are easily dealt with too.   

[Barrett]

My V&H sideshots had a little pop. I installed some BCT quiet baffles and it went away.
They had the lollipops in them. Just adding the lollipops to your pipes might help.